Engine Control Unit

After a few weeks of running very poorly, my local service shop has informed me that after 3 days of looking and many tests they have narrowed my cars problem to a faulty ... CIS Brain they called it.

The part number on the current part is 008 545 8132
My MB Dealer tells me that the new number is 011 545 2732

I'm in kind of a pinch here...The only way (they tell me) to test the car and see if that indeed is the problem is with another ECU. But, these parts are VERY expensive and once purchased you can't return them.

This is a 1990 300E 3.0

Is there now way to remove the ECU examine it clean it and maybe repair it?

I don't want to loose my 300, but these repairs are eating me alive!

Thanks
Steve