Running pex is easy, and if you get the oetiker style clamps (http://flairit.publishpath.com/howtouse ... xcrimptool
) the tool etc. is relatively cheap, and it's all available at HomeDepot.
The real problem is the hot water source and you can either cut a hole in the van for a Suburban or go with the Espar. Or live without and/or use a stove. Depends on if you're more comfortable cutting the body and running propane line, or cutting into the fuel system.
If you can't live without hot water, it might be a deal breaker- not impossible, but not quite as simple (in my opinion) as running 110v sockets and putting in an inverter.