I can't swear to this but I think Dodge dealers can still work and get parts for Sprinters as they were sold with the Dodge badge.
We bought our 2007 RT RD Adventurous with the 2006 chassis and the 5cyl engine. The MH had only 10k miles on it and we paid $50k. It looked and ran like new. We recently did a trip from the Oregon Coast to Quartzite, AZ then up to the Grand Canyon. We continued up through Salt Lake City and Boise, ID and then at Ontario, OR came across US 20 to the Oregon Coast. We drove between 65-75 MPH when we could and averaged 20 mpg. The Sprinter ran flawlessly and handled great I drove it on Hwy 89 in Arizona through Prescott, Jerome and Sedona not an easy road to traverse but the Sprinter went over it without a hitch. As I understand it the 5 cyl and 6 cyl have the same horsepower, the 6 cyl has slightly more torque. The 5 cyl gets 2-3 more mpg than the 6 cyl. We are very happy with our purchase.