a lot of people new to campers or coming up from tenting, i'd suggest they record the important parts of their PDI with their cellphone, esp things like lighting the furnance/troubleshooting the furnace, adjusting the thermostat, waterpump, using the how water system, winterizing and doing the HW heater bypass...
it may be easier for you to refer back to a video visual aid those first few times than try to remember what the dealer said while you scan the basic manuals provided.
there is a PDF link in this forum for almost all of the equipment manuals associated with the A-frame units. good to have on a phone or tablet in case you need it. its not that easy to go through the several manuals provided on delivery.
take some time to camp in it a few times before you start buying all sorts of stuff and modifying it - different campers have different needs.
realize you probably dont need as much stuff as you think you do. youll probably bring everything but the kitchen sink the first few times - keep track of that and things you dont use after several trips (unless they are emergency items not meant to be used often) you can then decide to take out or pack only seasonally or situationally.
the a frames are a joy to setup and takedown - very easy. grab and go. the more stuff you take, the more setup, organization, transport and hassle ... for me anyway - so i try to keep it as simple as possible without any major sacrifices or limitations. im not trying to reproduce my home, more like reproduce what id get in a hotel room or efficiency apt when traveling - all the basics but none of the fluff.
id suggest spare fuses (a small kit of assorted fuses is fine), a few different lengths of water hose, a fire poker and a way to test your battery capacity.