Unless you know a mate who's a spray painter or you're willing to do all the prep work yourself, I'd budget around $3k to get something decent (ie. people don't say it's a crappy paintjob).
Well, that's what it cost me up here in Qld anyway. Speedcore also got someone to do his for around the similar price range as well ...
As for replacing the sealing, um ... I keep the originals as I couldn't find new ones. Same goes for all the clips etc ... not sure but I doubt if anyone supports Sprinter parts in these areas ...
Toycelica 77's right ... your car will be out of action for about 3-4 weeks. It'd be cheaper if you resprayed the car the original colour as well ...
On the other hand, removing rust & dings etc could blow your budget out ... my car had no rust and was a fairly straight example ... it was the labour which cost me.