Sure, why not. I made connectors for the 91 clocks so I wouldn't have to cut the factory harnesses on my 88, 89, and 90. I like the five segment 91 clocks since they match the left side panel.
It's just a light that triggers at certain mileage (80k???) to change the O2 sensor but does not mean anything is wrong. I recall a write-up on resetting it but most people just remove the little control box.
@Rwhip I second watchamakalit's statements. We're all here to help if you need it: advice, parts, etc.
Welcome and add yourself to the original owners thread, I think you qualify:
An MJ/XJ shifter should fit. It separates from the shift tower, some have done it in place using two pickle forks (may dent your trans tunnel), search YouTube I know there's at least one video. Here's what the connection looks like.