These Sprinter vans are service vehicles designed for lots of urban miles so while they aren't bullet proof, they are pretty reliable. Even if you never drive long uphill grades, the turbo resonator fix for the T1N is a must for the piece of mind it brings.
The other issue to look for when purchasing a T1N is something called Black Death. It's some sort of carbon buildup around the injectors. It's common to the MB inline 5 cyl diesels but unlike the name, it's not fatal. There was never a recall so it may be like many issues that get over represented on the internet.
Here is a good pre-purchase checklist for the Sprinter chassis:
Sprinter RV: Buying a Used Sprinter – Top Ten Problems to Look Out For
There isn't as good of a coach checklist however Interblog's blog shows many of the repairs/upgrades that we have done.