I'd try www.sprinter-source.com for real, first-hand resources on that. There are a lot of opinions good and bad. I'll go in order:
A: Sprinters are the top of the pack when it comes to luxury features such as lane departure warnings and automatic braking.
B: Varies. Here in Austin, there is a very good Sprinter dealership, as well as a Freightliner dealership. However, some other areas may require driving hundreds of miles, only to find the Mercedes place only services cars, or the FL place only does big rigs.
C: This is an "ask three people, get four answers back" question.
D: The Sprinter Source forum has a poll on this exact topic.
E: Not much to choose from now, but later this year, it will be a toss-up between ProMaster upfits, Transit Upfits, and Sprinter RVs.
As for a Sprinter van, got more details of what you want to use it for? Something that would be an ideal fit for me would probably drive someone else absolutely insane.
