1994 C280 replacing serpentine belt and alternator

Hello all,

I'm interested to see if anyone could help me with how to go about replacing the serpentine belt and alternator on my 1994 C280. I had the serpentine belt changed by a not so bright mechanic and suspect that he installed it incorrectly. It's loose right now and I'm thinking that the automatic tensioner is not working because the belt was incorrectly installed.

Can anyone help out? Thanks

Jonathan Evans
NC