The issue with idling is that many Sprinters were being used as delivery vehicles, and the drivers would drive them a block or two, then idle, then drive a block or two, then idle, repeat-repeat-repeat -- you get the idea. These vehicles were not designed to spend a great amount of time idling, with another large portion of their lives running at low speeds for short periods of time. Damage was incurred, until the American companies figured out ways to get around this. Keep in mind that in the land where these were designed, letting a vehicle idle for anything more than sitting at a traffic light is illegal. Or to put it another way - these were not designed to spend a great portion of their lives at low idle. A high-idle mechanism solved this problem.
Because of this issue, people now think that a Sprinter can't be idled. Even here, there are people who continue to perpetuate that misbegotten notion. A Sprinter can be idled if you get caught in a traffic jam. You can idle it for hours if needed. You just can't drive it all the time at low speeds for short periods of time (engine never has a chance to warm to normal operating temps), and then leave it idling over and over and over.
As for maintenance centers - yes, there are not as many as Ford or Chevy. However, they are out there, and if you are worried about a breakdown, get a breakdown service that will tow you to an authorized service center. If this is an issue for you, then you should look elsewhere.
Oil and filter changes are extremely easy. You can order OEM filters online for about $12, and oil for about $8 a quart. Be warned that these use about 13 quarts. We have had our Sprinter for about three years. Not counting oil changes, we have spent about $400 on service. Our service costs have not been any more than what we would have spent on any other make of chassis.