I would start out with replacing all fluids/filters everywhere;
-trans oil
-engine oil
-rear diff lube
-radiator coolant
-brake fluid/flush
-p steering fluid
-oil, fuel, air filters
Then I would tackle the rubber;
-check tire date codes (over 7 years replace)
-belts
-hoses
-wipers
-door seals
-vacuum lines
After that, I would look at all replacables;
-brake pads/discs/drums
-coolant thermostat
-water pump
-having injectors cleaned
-exhaust
-brake lines
-battery/electrical connections/grounds
-lighting/wiring
Spending a few more hundred $$ upfront, and getting it completely reliable will save you potential thousands $$ later at a repair shop, not to mention the hassle of a breakdown in a desolate area, or being without a place to stay while in the shop. You can build out the van however you want, but securing it's reliability is paramount to keeping the good times going....have fun !