I usually don't post (garneska, my better half, takes care of that), but I'm the driver of our class A and had some thoughts for you. Kris and I have only had our 41' class A since July 2014, so learning to drive it was a challenge. As a (relatively) new driver, here are my thoughts:
1. Yes, people are going to watch you back in. It's a fact of life in campgrounds. Most of us won't be judging you - mainly because we've been in your shoes before, trying it for the first time.
2. When backing in, don't be a hero. You don't get style points. My first experience backing into a site involved me smacking the entry door into a tree. Thankfully, there wasn't any damage - it was very low speed. That being said, take it slow. When in doubt do the following: 1. Stop 2. Exit the rig and see exactly where you are 3. Formulate a plan - even if that plan is starting over.
3. Backing into a site can be trying on a marriage. Keep calm. Kris does a great job keeping an eye on any hazards around me while backing.
4. Again, just take it slow and when in doubt, stop, look, plan, and restart.
5. Other campers may try and help you if you seem to have issues, if you don't want their help, just be polite. I tend to find it distracting rather than helpful as Kris and I have our methodology.
As for loops, I would say from experience that 700 is easy to get into, although the turn coming out can be a bit tight. 800 and 900 were doable as well. From just walking the loops, 600 appears to be the easiest, plus you see big rigs (45') there all the time. 400 and 500 seem tight to me (plus we saw an Essex clip a car in 400).
Dogs are another question. Yeti (look at the January trip report if you want pics) barks at everything. So it doesn't matter where you go. Dogs are always being walked by your site - dog walk or not. The difference between being on the dog walk and not being on the dog walk is minimal from that perspective.
All that being said, welcome to driving a big rig and enjoying learning to drive it. I will say, it does get easier, but it's taken me a year and a half of driving (and ~5,000 miles under my belt) to say that.
Bert (garneska's DH and driver)