First let me say,

to the wonderful world of camping and the "Fort". As long as you have an open mind and enjoy nature, I am sure you will love it.
We are just 10 days away & starting to get in the thought process of our Ft Wilderness visit.
We are traveling in a 45' Prevost. I have reserved a Premium spot. I have completed the online "check-in" page (still not sure if I did it right as there are no instructions).
Awesome. I am Jealous... I have much longer to wait. I cannot provide much advice on the "Early Check-in" process as I have not yet done it, but I imagine, it's more of just an "Acknowledgement" of things as well as providing payment information for the record (for incidentals, etc...). I would imagine that you could/would probably still stop at the check-in area when you arrive and the process would be much quicker for you.
We have taken our bus out the past 4 weekends as "practice".....otherwise we are really new to using it. The first 3 weekends we just lived in a parking lot and got used to the systems. This past weekend we were at a campground - but because it was snowing, there was no water/sewer.....so we have never tried that.
My biggest advice here is first, make sure you have a hose for Potable Water (Typically they are WHITE). While as kids, we would always drink from the green house (at home) when RVing, the green hose can have a tendency to be used for other things (like Flush sewer hoses). Using the White hose makes a CLEAR distinction that it's not for that. DO NOT use the green hose at the sites for filling your Fresh Water tank.
This probably won't be an issue at the FORT but it has for us in other places. We have an EXTRA water hose too because the distance has been long in some cases and it was needed. Also the Fort has EXCELLENT water pressure. You WILL want a
pressure regulator. (We found out the hard way on this one) for your RV to protect your lines. Don't worry, it won't regulate it too low. Many of them at
Amazon relatively inexpensive. We have the Valterra A01-1120 Brass Water Regulator and it works well.
The sewer hoses are fairly basic. Now I only have a TT and from what I have read the some of the Class "A"s can have more then one connector for dumping (Black and Grey). For us it's one connector. My best advice here is that the connectors are pretty basic and are "Gravity Fed" so don't run the hoses UP hill. When hooked up, don't leave the black water tank open. Allow it to "Fill" as this makes it better to empty (think "Momentum") also it allows TP a better chance to "Dissolve" better. I have had dealers (and manuals) say that if you are hooked up to a sewer at a site, that it's okay to leave the Grey water open, but I also like to let it fill up. That way when I flush the Black water tank, I can then "Clean" the line/hose with the "Grey" water.
I guess it goes without saying (or at least I hope it does) to use appropriate precautions. (Gloves and such.) Also probably want to make sure you want more then 1 section of sewer hose. I have 3 sections and it just fits in the bumper storage. That is typically good for most areas.
In all cases, there was no backing up required. My dh is nervous because Ft Wilderness only has back in spaces.
When we arrive, will someone from the Fort escort us to our space and help guide us in? What if we can't get into the space? (I've watched
YouTube videos and see that "neighbors" can be parked in the way. Then what?) We won't have a tow vehicle, so unhitching and driving to the space is not an option.
My dh would prefer a space that allows him to see the space he is backing into from the driver's side (if that makes sense). Is there a way to get one of these?
Yeah, backing is always an issue. Does your Prevost have a backup camera? That and a helper helping to guide you can be invaluable. I will tell you that many folks at the fort, while very friendly, also take joy in watching others try and park their rigs (regardless of Class A, 5er, TT, PUP, etc...) but will also often offer assistance. Cars aren't supposed to be parking on the roads and are to be completely on the sites. Premium spots will give you more room to park your rig, but the roads are still basically the same.
As for a spot that your DH can back into where he can see on his side, I can understand this, but it's hit or miss. The Sites are generally in a "Loop". As you enter the loop (all seem to be ONE WAY) you go to the right. Sites on the "Outside" of the loop will of course be on the Passengers side, those on the left will be on the drivers side. You got a 50/50 chance at either. With the Class A though (and no Tow/Toad), I would imagine it won't be that much different particularly if you have help (and cameras). As Bishoparc mentioned. FRS type radios can work great helping this too.
If a spot is "Impossible" to get into, You can always go back to the front and request a different spot. Just make sure you let them know how large your RIG is and how many slides you may have.
If we arrive early......will they accommodate us, or will we be hanging out in the parking lot until check in time?
If the site is available, they will accommodate you, if not they may offer you one that is available (if they have any at that time) otherwise you can park in the overflow lot and go enjoy the parks using their transportation (or whatever) or you can drive you Class A and go do... well whatever. If you leave them a cell, they will Text you your site number when it's ready.
Sorry to have so many questions. We had such a lengthy conversation at dinner tonight. There is so much we don't know!
No worries..... You have come to a good spot to get questions answered. While some of the answers may seem conflicting, really it's just a different way that people do things based on their experience. That is how you get to KNOW what to do.... Just relax and enjoy. Even when you get there, if you have an issue, most folks at the fort (Guests and CMs) are willing to help you out however they can. Just ask if you need it.
You should be fine with the premium spots backing in. Most folks that stay at the fort are very nice and will likely help if you need it. If they're in the way you can ask them to move but typically security keeps a close eye on stuff like this and keeps people out of the road.
So true. The funny thing is, is that our first trip to the fort (300 loop) we came in late (it was dark) and people in the sites around us were, shall we say, over flowing their sites. While they were friendly, I struggled to get our TT (31' tip to tail) into the spot. I didn't know the rules at that time and I wish I had found the DIS boards before we went. Anyway, it all worked out in the end and we had an awesome time.