Just to clarify one issue, has anybody found an RV dealer yet that sells DP's and also has a repair facility for the chasis? Not saying they don't exist, but I've never seen one here in California. Maybe the dealer can change the oil and the filters, but any significant repairs and you're taking your DP to a Freightliner or a Cummins or a Cat service center. The dealerships still have service centers and service writers, but it's all for the house part of the RV.
And to the OP: I find it very difficult to believe that an RV dealer would sell you a 13 year old motorhome, let you take it off the lot, and simply authorize a blank check for "whatever" you find wrong they'll fix.