You'll need some insturment cluster removal tools (or you can fabricate your own from wire coat hangers or similar)
such as these:
Then check out this DIY article:
http://www.peachparts.com/Wikka/W124InstCluster
Its very similar except that your w202 has an electronic speedometer so you won't have that big screw on cable in the center. There should be enough slack to pull the cluster out a bit further.