We're picky, so I request a specific site in a specific loop. Actually, I list 3 sites that would be perfect for us and explain why and ask very, very nicely, and I always get one of those

Somewhere around here is a fax number, and I fax my request 10 days in advance of arrival. Also, there's an app out there that has video of all the sites as you go around the loops and lists site dimensions....I can't recall the name of the app, but you can probably Google and find it.
We like the 900 loop, which is close to the Meadows Trading Post, so for internet, I just take my laptop over there and grab a rocking chair or a picnic table and do what I need to do. I've always had plenty of company there in the mornings

I'm sure others know the procedure for getting it at your site...we never use it enough while we're there to make it worth the effort.
I've never done early check-in. When you do check in at the Fort, just let them know if you need help backing in...I'm sure they'd rather send someone over to help than have you take out a fence or something. That happened while we were there last....someone had a tough time backing up a Class A near the entrance to 900 and knocked out a few fence sections. Somehow a fence section actually got caught between their back tires and caused a bit of damage to the RV. There were a lot of staff involved and flashing lights and closing of the loop while they got it all straightened out. So don't be afraid to ask for help if you think you might need it!
Have a great trip! I would love to be 25 days out from my next one, but it's more like 575 days for us, lol!