Your blackout is probably loose or corroded battery terminal related. You're going to have to disconnect the battery and thoroughly clean the terminals and the faces of the lead sockets on the battery with baking soda and water.
I have seen batteries leaking through cracked side terminals so wear gloves and don't wear anything you don't want acid holes in. I have clothes I paint and drywall in. Battery acid holes will just add character.
The other problem a lot of folks run into is the PO replacing the battery bolts with poorly fitting aftermarket parts to install audio and other equipment rather than properly installing the power connections to the threaded post in the fuse relay panel. These bolts typically don't have the wide umbrella under the head that the OE type bolts have, so the terminal contact area is too small against the flat lead battery connection.
The other common battery terminal problem is ham handed Vise-Grip mechanics chewing up the hex heads on the battery bolts with pliers and even stripping out the battery post threads.
Diehard 45172 or Deka 05323 are properly machined GM type replacement side terminal battery bolts.
The original type side terminal battery bolt heads are 5/16" or 8mm hex. 8mm & 5/16" are close enough that either size wrench will fit.
This is the battery bolt you want to see.
Oil.
Not starting a holy war here.
5W30 is stated on the fill cap. Use a decent synthetic or semi-synthetic API SN or better motor oil. I'd make sure it meets the DEXOS rating as well.
Axle ratio.
Look at the SPID (Service Parts ID) sticker on the glovebox door. You should see at least one three digit RPO (Regular Production Option) code that starts with G. G80 is a limited slip axle, if your truck is equipped, but the other "G" RPO will likely be your axle ratio. Post a pic of the SPID sticker in this thread... with the VIN redacted if you're worried about it.
Transmission
Likley you have the 4L60E or 4L65E.
Paint adhesion issues.
Low VOC and water based paints from 1980-2015ish seem to suffer from adhesion issues to varying degrees. I've seen this on newer rigs, so it's not fixed across the board. Lighter colors seem to be worse, but all of them seem to have suffered from adhesion problems. Why did it take 30+ years to fix this and it still ain't right...?
The method the guy in the below video used should give you a socially distanced paint repair that won't allow body rust to set in and won't draw attention to your paint adhesion problems.
I would mask off the entirety of any glass near the paint area, especially the windshield. You can remove overspray with 0000 steel wool, but you can end up with spiderwebbing. If you already have a bunch of sand pitting, and you're replacing the windshield, then don't worry about it. It's less work to mask and not have that problem to begin with.
http://youtu.be/zwHxCF7W6Ks?si=sWORrKVqP6zqF7m-