It turns out in my 2000XJ I do have an OEM keyless entry circuit board under my dome light. I wasn't supplied with a key fob so I didn't know. I'm not sure if it's any good and I wish there was a way to test it, but from my understanding, all I have to do it buy a key fob and have the dealer (or I've read you can somehow dyi) program it and hope the circuit board isn't fried? I'm guessing if it is I can get one at the junkyard and see if it works?

A couple other small questions...
I know this may sounds dumb, but I noticed two different colors for the peanut style fob, grayish and black. Though they are probably the same, does anyone know if the XJ got a particular color of the two? I like to be "original"

And though this isn't original... Are you able to use, say a 2004 WJ keyless circuit board in an XJ? Or is that a completely different harness? I heard the range on these are better.

 

Buy a cheap alarm/remote starter, much easier solution.

ETA: Not sure what a WJ circuit board is "Whamma Jamma"?

 

Thanks but trying to stay away from aftermarket. WJ keyless entry circuit board, if they have them like the XJs do under the dome light.