Most important thing is to take your time and make sure everything is to YOUR standard. IMHO, its much easier to get the repairs completed if the unit is left sitting at the dealership. That way there is no question of what was or wasn't correct when it left the lot.
I used this helpful document
as a guide for my most recent PDI.
Great idea to take a second, knowledgeable person along. My girlfriend accompanied me and though she doesn't know much about RV's, she has a eye for detail that I tend to lack. That was very helpful. I also had an excellent tech for the walk-thru but that can be hit or miss for each individual. Not much you can do to control that I suppose.
Good luck with the delivery and be sure to post up some pics of your new TH when you do get it home.