You may check out this
http://www.************************/BitMapPage.aspx?bitmapid=228&bitmapname=Exhaust+System
The gasket you're talking about may be left to No 132.

The instructions to replace the distributor can be found here:

http://skinnerbox.steaky.org/Service/W124/Index/103/15EngineElec.htm

File 15-3010 to download.
Good luck, Bruno