I think that you never need it. Because , it has no belt, it has chain instead.
belt
Need a picture diagram of poly-v belt routing for a 1999 Merced es Benz C280
It has a chain for timing. There is only a poly V belt for A/C, alternator, and the other accessories.
There is an electrical connector located under sear that connects to seat belt buckle, just disconnect it.
Take it to a mercedes garage
how to change timing belt mercedes benz E200 1.8L 2008 model
how to change poly belt on 2003 E320 mb
it has a timing chain no need to change it
how to change the v belt on c320 mbz?
Mercedes c200 cdi hasn't got timing belt. Has got chain.
How much it is going to cost
Don't know looking for instructions.