Fuel reserve warning light stopped working a while back so (after confirming continuity of the yellow/blue wire from the sender to the light) I changed the sender and the issue has been resolved. I used a replacement unit from @zcardepot.com which is of excellent quality, has the exact same factory connections and cost $78 (compared to the unit offered by MSA at $200 plus you need to splice in a different connector!!!).
I made a wrench out of 2" PVC pipe to turn the lock ring very easily, which makes the whole job a breeze. With a Dremel, I made 4 slots on the inside edge of one end of a 6" section of straight pipe to coincide with the 4 crests that jut out from the top of the lock ring. A 90 degree elbow at the other end of the pipe makes for easy turning.
I also cleaned up and painted the edges of the access port with bed liner, and replaced the weatherstripping foam on the inside of the cover.
Pics below.