When you say "dash", I suppose your are referring to the instrument cluster. There are no serviceable parts inside the cluster, it is a complete assembly. The mileage is electronically transferred by using MB software to your new cluster. That's the bad news.
The good news is that 2000-2006 MB S-class and CL-class vehicles have a ten year/unlimited warranty on this part. Your car may still be covered; call your local MB dealer today!!