We just bought a 300TD, and the blower motor quit on me on the way home from the purchase! (in the rain, in rush hour....
). We took the blower motor out to check the brushes, but it looks like the armiture is shot. I think most commonly it is a brush problem. There are brush repair kits on ebay. We bought a used blower motor at the auto wreckers. If you can find someone who is parting out a car, that might be an idea. I would try the blower first, before the climate control as it's cheaper, and very likely the source of the problem.
Good luck, and enjoy!