Parts can come from Jayco dealers (expensive), sources like Etrailer on line, and used parts from various RV junk yards around the country. Doors you might find used but trim parts are still made and just a matter of research online or at a local Rv parts store with pictures, measurements and descriptions. Don't forget Ebay as there people out there parting things out.
Here you should post a picture(s), measurements, and a good description of what it is used for and you may find someone who needed that same item and found it.
Also, try the search line above to find any threads on rebuilders of your or similar models. Good luck, did it myself years ago. On the wiring, you may just have to get tape and trace every wire to figure out what it is (12 vs 120) and where it goes and start from scratch.
2017 SLX 195RB
2021 Jeep Grand Cherokee Summit L 5.7L V8
Andersen WDH hitch, Renogy 100 AH Lithium &
200 Watts solar panels from Renogy
Prev. '14 Jeep Grand Cherokee Overland, gas 3.6 V6