Hello -
Well, MB doesn't release the parts info on that to us..........not even the labor estimation as you see from the pic below.........

I checked another source for the ECM (I have attached the web site for you and it only has the years from 1972-1985.
http://www.thebenzbin.com/products/index.php?N=1668&Ntt=electronic+control+module&No=10&Npp=10
So I hate to say but you are going to have to check the dealer on this one or someone in your area that works on MBs. Get several estimations.
Next - you have to see if you feel the car is worth it to you. How is the interior, the outside, the paint, the engine.......is this the only problem you have had.........can you do t this financially. That is something you will need to look at.
I attached an estimate of NADA guide for you..................

Also, let's say your car is not in good shape (no offense) there is the cash for clunkers program. Many Dealers in this area are doing this...........
Here is the website on NADA that gives some info on it. Check with your local Dealers
http://www.nadaguides.com/default.aspx?l=1&w=21&p=44&f=5791
Hope this helps
Aug 19, 2009 at 9:03 AM