I worked on an 89 and what I did was unhook the negative connection to the battery and leave it off for 15 minutes. The reconnect it. You will need to fix the time and radio channels but normally the computer is reset
If you are referring to resetting the Check Engine Light then you will need to have someone with a scanner to do it. If you are referring to reprogramming the Engine Control Module then the dealer...
the older cars u can unhook the battery for 15 minutes but with the new computers in the cars today u have to unhook them for 30 to 45 minutes then it will reset the computer
I found the following on Auto Zones website - you can register for free access to repair guides .
GM Bonneville/Eighty Eight/LeSabre 1986-1999
Stored fault codes may be erased from memory...
you can disconnect the negative cable at the battery for at least 30 seconds. if the problem is intermittent, the light will be out afterwards. if it comes right back on, seek a shop that does engine...