RE: rear wiper
The rear wiper is DIY serviceable. The motor should be fine. I suspect that the wiper shaft that passes through a sleeve to the outside of the vehicle, that the wiper arm attaches to, has seized in the sleeve. You can take the gear housing apart, tap out the shaft, sand it clean, lube it with a good water resistant grease, then re-assemble it. I did mine and it works fine now. I too was getting the gear chatter, which was the wiper motor driven gear clicking on the stuck gear of the actuator arms that is supposed to move the shaft. It's not hard to fix ay all. Just take your time. Good Luck.
1996 LT Blazer 4x4 - 130,000 miles and still going
Old enough to know better, but still willing to try!