Electrical failure S13 240sx hatch

[JD_Stance]

Hi everyone. My first post so go easy haha. I bought my 91' 240sx a couple of weeks ago and it's been perfect to me so far. Bought it off a Nissan dealership with 68,000km so about 42k miles. It was owned by an old retired couple and garage kept for the most part. It has some minor issues but none that are troublesome. Until now, the electrical a have just gone on me and I tried searching around with google and everyone send to be having different mixture of problems but none of which are the same bunch as mine. So I'll just list them I guess.

Things that do work.
Dash lights (when lights are turned on)
Headlights, the amber lights, and the daytime lights below the amber
Brake lights
Reverse lights
Windshield wipers back and front
Door and light chime
Map and back seat door lights
Hicas light and over drive light (yes it's auto, no idc because I'm still in high school and it's my daily)
Radio and radio antenna (actually the stereo is broken but it still lights up and scans for stations but it just never plays anything)

Things that don't work.
Tach, speedo, all service lights on dash
Power windows. God help me cause my car has no AC and it's hot as hell out
Turn signals

I've done the sleepy eye mod where you pull out the popup lights button and snip the brown wire and put electrical tape on it, but something tells me that isn't the problem and it's been running fine with the sleepy eyes.

Please help, I've taken it to Nissan Service dept and the guy said he never heard anything like it and he said it'll cost $135 an hour an inspection.