can't figure it out

93sc, auto,........while driving or at idle my rpm gauge drops to zero and the check engine light comes on, then it will go back up and fluctuate and the light usually goes back off. I also feel slight vibration from engine while at idle (sometimes). I believe it may be my coil pack or DIS module. but I'm not sure. I also use a lot of brake fluid, but I never see any leaking on the ground. Could anyone familiar with these problems help me out. THX

You need to check the codes first.

I had the engine diagnosed...it had trouble codes stating loss to tachometer. The technicians were very vague as to what needed replacing. They stated it could be a number of things.

Well I dont doubt that but I need the code #'s to be of any help.
You can pull the codes yourself.

Cam sensor, maybe?

these are the codes. 124-tps voltage (replaced), 212-loss of idm to pcm, 214-cid ckt failure. How do I check the codes myself?

Start with replacing the cam sensor (aka CID sensor, as in code 214 CID circuit failure). I suppose it could also be the DIS or the wiring harness, but this is an extremely common issue with the SC, and it's almost always the cam sensor. Lucky for you it's a cheap $15 part you can replace yourself in ten minutes, so you don't need to go back to your mechanic, who doesn't really sound like he knows what he's doing.

Then see if the code 212 also disappears after the cam sensor fix. If not you might have a bad DIS or other problems, but worry about that later.