I purchased a harness from here: GTW Negative Switching LED Harness / Power Upgrade, Ultraflex4x4 Official Store - https://www.ultraflex4x4.com/ecommerce/product_info.php/cPath/26/products_id/41
I didn't spend the time to figure out how to wire them up on my own, but maybe the info/pictures...
You can see the servomotor just by pulling the radio out. It will be on the top. It is difficult replacing with radio removed only, but it can be done. I have been dealing with a similar heat issue to yours and have given up getting it to work. Interested to see yours getting fixed.
I've had luck with this knock sensor from autozone. Was $21 when I bought it in July 21 and no codes since. Price has gone up though.
https://www.autozone.com/engine-management/knock-sensor/p/duralast-ignition-knock-detonation-sensor-su5813/364506_0_0?searchText=SU5813