It appears you have started in the right place by reading the Owners manuals.
The big thing at PDI is to make sure they not only show you but allow you to perform some of the basic stuff, like setting the jacks and letting out the slides. Make sure you understand what has to be done in which order and which doors have to be in what position if you have that type of slides, also the bed position if it has to be up to let the slide in.
Have them show you exactly where the cutout switches are for the chassis and house batteries. Make sure to start the generator and divorce from shore power and see if everything still works, the AC's the fridge.
Have them show you how to fill the Potable water and dump sanitary.
Turn on all of the TV's and see if you can get them to work from different sources, bring a DVD with you. Check out the stereo system, all the speakers every where.
Now when you get it home take it camping and check out everything else you could not check at the dealer and make a list of what needs fixing or replacing, every light, every door and lock, every switch and button, the washer and dryer. If you are handy you can fix some of the things your self and just get the parts from the dealer. The other things set a date to drop it off and plan on it being there awhile for the big things.
If you have Satellite make sure you check it out also, on every TV.
Remember the Owners Manual will cover all of this but knowing is half the battle.
Now go and enjoy your new Motor Home