1998 Buick Century

Electrical problem
1998 Buick Century Automatic 106000 miles

When I shift out of park to anything else the background light of the gear I am on does not show up. It failed inspection for this. My mechanic tried putting in a new clutch and he tried changing the computer but nothing worked. What is causing this?
Also, when the gear change worked, it would lock the doors while changing gears. None of that works now. It only works when you are in Park that it lights up that you are in park and it unlocks the doors.