For the door cylinder, my '96 E came to me with a nonfunctional one. I removed the cylinder from the door (one bolt) and there was a pin missing (probably broken and sitting in the door) that turned the shaft. I used a small cotter pin from the hardware store and now all is well. The single bolt holding the cylinder in place is accessible by pulling a bit of the door seal out of its groove. There is no need to pull the interior door panel.

What's wrong with your keyless entry system? It took me a while to notice that my lock cylinder was inoperative.

As for the SRS light, I have no idea.