I am not the brightest with computers. I have to post with my phone and then get on the computer to spell check and correct. Bad eyesight as well, yea!!! These gasket are not cheap but work really well for me and I think most recommend the same. I also see you are into your flywheel. I eventually have to pull my tramsmission as I have a rear main leak on mine. It is gradually getting worse. Go ahead with a new rear main seal while in there.
I see you have some engine codes. Luckily I have not had to dealwith codes yet. It has been so long since I have had to pull codes on one of these, it is something I have to relearn. Eventually I will. I have seen code readers for these and they are really cheap.
Some of your electrical issues can be grounds like you mentioned. There are more then what you may think. If you want to go thru my build thread, I try and show all the grounds that you may not be aware of. Battery cable has 3 points of contact alone on it. There are lots more grounds then just battery cable. You have one even going to your washer motor.
If your injectors connectors are shot, I found a place that sells new connectors. I cant remember it but will eventually get it.
Seeing you are new to mechanics, a 4 cyclinder motor is not just plug and play and doing a motor swap with a different motor is something I would not recommend for a beginner. Easiest thing for you would be to get a 2.9 motor from a boneyard or similar. Even years of 2.9 have differences. 87 has an EGR tubew where as 88 does not.
Also on my build thread I show the Ignition Switch under the column. It can cause a lot of electrical problems. I think I show quite a bit on it. It is an easyfix and pretty cheap. The head light switch that controls your dash lights and cab lights is not an expensive fix. I still have problems getting the tab to release to get the knob out. I seen people just reach up there and have it out quick. Not me, I get to fool around with it for a while before getting it out.