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you can separate out the "roadtrek" parts like the body kit ( if applicable) and anything custom made for/by roadtrek
most of the appliances and energy systems are likely used by other RV manufacturers ( ex dometic fridge, thetford toilet) and if so, parts available widely. Some of these items have been used for years.
and the "van" parts will be available from the van manufacturer ( ford, chev, MB, fiat/dodge etc)
There will be a few foibles and some of the R/T owners of those models will be able to point out what to watch for
some of the sprinter owners can talk about any issues, some have emissions control problems/costs
( I have an 2006 pleasure way on a chev, the only parts I can think would be an issue would be if I damaged some of the fiberglass bodywork- the chev part can be fixed anywhere by anyone with parts from napa- the appliances I have are all simple & commonly used)