instruments guages suddenly fail?

[WANT '71 280SEL]

I am referring to my '87 300SDL. I parked the car for 5 minutes while I ran into school and after restarting the car, none of the guages worked. I didn't notice until leaving the parking lot and later today I've noticed some other non-functional items. For instance, the A/C compressor won't come on but the blower works, the only warning lights that come on is the:GP, antilock, ABS, and alternator. There may have been one other light that comes on, but none of the others do (low oil, low washer fluid, seat belt). They won't come on when the key is in the "on" position while waiting for the GP light to go out. Also, the odometer isn't counting and I think this just started, but while the car is idling with the LF door open, the warning buzzer sounds. I don't think it used to do that.

Now, as far as diagnosing, I have checked and double checked the fuses to make sure they aren't the culprit. I also made sure that other components sharing the same fuse worked, and they did. I even switched fuses around to no success.

This has produced no warning signs. 2 weeks ago though there was one or two times that the oil pressure guage didn't register for the first 5 or 10 minutes of driving but all was fine earlier today. A month ago I repainted the needles, but like I said, everything's been fine. 3 months ago I replaced the electrical part of the ignition switch to cure a problem of the key not fully reseating after cranking the engine. I've moved the key around to see if that would help since that's how to diagnose a key switch and still nothing would happen. Please help as this is very frustrating for me. I just got the car running after being down for a week yesterday, now this!

Thanks
David