Hi Melissa! We are also owners of a Class A motor coach so I completely understand why you would want to know details. Backing up and turning around in a big RV is not a simple task!
I am not sure if you have reservations to stay at the great
Fort Wilderness Resort. Please consider this if you have not as it is one of the best RV resorts in the country. The amenities are immense and you are considered equal to any other Disney resort guest but you just bring your own room.
If you arrive early and your spot is not open you are welcome to park in one of the few over flow areas at Fort Wilderness. You can park and then hop on a bus to your destination and have your check-in completed so all you have to do is return and move the RV. The same is on the last day of your stay. Check out is 11am but many guests still want to enjoy a park day. So pack up and park once again in one of the resort over flow lots and use Disney transportation to get where you want to go and return back to Fort Wilderness.
Now if you are not staying at Fort Wilderness you can park in any of the Theme Park lots and the cost will be $22 for an RV. Again if you have a resort reservation you will not have to pay. The attendants will direct you to the place for the large vehicles and just know you are not allowed to keep a generator going while you are in the park. If you have pets this would not work especially in the warm months of Florida.
Hope this helps and let me know if you need further information!