Hello KatheK -- I too am relatively new here on this forum but not too new to TC. We have a 2006 Outfitter Apex 8 SB on a 2006 Dodge RAM 2500 CTD. I've done a fair bit of repairs, work and modifications on the Apex 8 and while I don't admit to knowing it all (by far), I'm willing to help whenever I feel I can.
Just do the normal RV checks you would do on any used RV then check for smooth operation of the mechanism to raise/lower the pop-up. When the pop-up is down and latched, look at the seal and for any gaps between the upper section and lower camper structure. Make sure everything is even and straight on the upper to lower seal. Pop-up and down should be smooth and easy.
Good luck and enjoy the new rig.