First let me correct something I posted yesterday: Auto Trucks Electronics can be found at autoecu.com or 800-257-3359. Sorry for the wrong info.
Second: I did replace the coil during my "trouble-shooting" stage because it was nasty looking/old and not too expensive - a cheap fix if it worked, but it did not solve the problem. I would think you should not have a problem finding a module for a 1988 300 SE as that is a 103 motor? and many more of them were made than the 300CE as well as the module being much more simple and cheaper. I would recommend the following contacts: AutoTruckElectronics(see above)to check on a rebuild; SilverStarRecycling.com;EuropeanConnection(800-395-8636);EVERYBENZ@aol.com;MercedesDismantlers.com;MercedesPartsUsed.com;ActionSalvage.com;PotomacGerma n(pgauto.com);Parts-ToGo.com;QualityAutoParts (qaparts.com).
Cary