My 91 Sammie just quit running one day. After alot of checking it turned out to be the old leaking capacitors on the computer board trick. I checked the posts concerning the computer and they recommended two places to have the computers repaired. I checked those places and one wanted $250.00 and the other $185.00. I thought that was a bit high for replacing 4 capacitors and checking the board over for broken circuits. I took the computer to a local TV repair and they replaced 4 caps. and repaired the circuits for $56.13. I urge anybody with a 90-95 Sammie to change the capacitors on your computer BEFORE you have trouble and don't pay $250.00 or $185.00 for a $56.13 repair. I pass this along with the hope that it will help somebody else.
With a used ECM, chances are that you will end up with the same thing that you already have.
Why not just replace the caps yourself? I did and it was not difficult. Took about an hour. less than $8.00 in parts.