I wouldn't say its very difficult. I'd probably use Conti (Continental) belts. They seem to have a good reputation. I also hear they have the correct 'V' form for the Mercedes pulleys. Don't know if that is bull or not. I can't think of any special tools. Also, loosen all the bolts for the alternator. I have heard the tension bolt is easliy bent. Mine was bent to some extent. The belts should have an inch to 1/2 inch of deflection in them.
Tom