I did a similar conversion. I bought a STOCK 2000 Astro AWD with 100,000 miles on it (4.3L V-6), and slowly started to convert.
I lifted it 2" with Overland Vans products.
Put some slightly larger tires on it.
Painted the lower "kick boards" and wheels with black bed liner.
Laid down some thin OSB over the carpet.
Made a bed that had storage underneath, and "telescoped out" towards the sliding door so two could sleep on it.
Made a cabinet for the back that held: Water (plumbed over to a pump faucet); stove, propane tanks, and cooler.
2" receiver.
Took a couple of trips to Maob in it (moto on a carrier in the hitch, MTB in the van) and enjoyed the tar out of that rig! Ended up selling to a co-worker, and going the "high top" camper van route with all of the amenities.