91CherokeeWhiteLimited

I'm a newbie, got a 1991 Jeep Cherokee Limited , white and I'm the orginal owner and yes I still love it. I've NEVER modified the Jeep or gone 4 wheeling with it and never been in any water higher than a couple of inches. I've had the oil changed every 3000 miles and never have missed this, ever !! Also from day one I have never put anything but premium gas in EVER. I have babied this Jeep since I got it brand new back in the Spring of 1991. As most of you know this was the last year the TRUE Limited came fully loaded with the big 6 cycle, 190 hp and all the power options you could thing of etc, etc. So I know the history of EVERYTHING on this vehicle ! And I can tell you its never been in a wreak and it has the ORIGINAL engine in it. It has 220,700 miles on it.
But a little more history...

Here is my problem, I have lost use of, a lot of electrical use of many different items ALL AT ONCE !
No power door locks, which also means no keyless entry, which means my keyless remote is now useless, no inside courtesy lights, no radio, no electric side mirrors work, no rear windshield wiper working, can't set the factory alarm system since I don't have power door locks that I use to use my keyless remote to hit when exiting the jeep. No factory digital clock working, overhead console stopped working, no map lights, no temp / compass is not working.
Things that STILL work on the Jeep are : all 4 door power windows, front windshield wipers, windshield washers work, rear windshield electric defroster still works, power seats work, parking lights work, headlights - high and low work, dash lights work, backup lights work, stop lights work, 4 way flashers work - and the dash arrows flash also when the 4 way flashers are switched on . My directionals work ( they didn't work until I finally replaced the Flasher unit in my fuse box. Horn works, AC works , heater / defroster works. Also my cruise control works perfectly.

All fuses under the dash are fine, as well as all fuses and relays in the the engine area ( PDC ) have checked out. Also I have no "check engine lights" or any dash errors coming UP

I have been living with the way it is for over a YEAR now, and yes a
year ago I took it to the stearlership and they had it a whole day and said it was the upper wiring harness ( that goes up the right pillar into the roof ) that has shorted or gone BAD and they can't replace this harness because you can't buy new harnesses for a jeep this old !! I don't know if this is the correct solution to my problem and need help. I have removed the headliner because I'm going to replace it, but need to address this bad wiring harness BEFORE putting the new headliner back up. I purchased a new craftsman digital multimeter yesterday, but I don't know electrical and don't really know how to use this multimeter, but willing to learn. Can anyone help me?
Sorry for the long history.