Hi there! I just started living in an 04 Chevy Express 1500 AWD with the 5.3l V8. Three months in now! I'm building and living as I go, so its a little ghetto but every week I chip away.
These are great, dead reliable vans, as others have said. Mine has 215,000 on the clock with very little issues to speak of. Waiting out for the V8 is worth it, and unless you plan on needing the increased payload that a 2500 or 3500 brings to the table, then I would also suggest gunning for the AWD too. I get about 15/16 city (light foot) and around 20 highway, which is slightly worse than the V6 but honestly well worth the extra power.
Hills are a breeze, oil pressure tends to jump around a bit but I have never had a problem with overheating, especially now winter is coming. Even towing. And highway merging becomes that much easier when you're faster than a lot of 4-doors around!
My only other advice is not to expect too much in the way of living space; you're going to have to be even smarter than most, because the vans just don't have the interior space compared to a Sprinter/Transit/Promaster. LOTS of folding furniture and double uses. And putting up the walls/ceilings in wood can be a pain because of the extreme curves to the frame. Otherwise, great reliable platform for a proper adventure van, and way tougher/more reliable than a Sprinter 4x4 too!