There's been some good advice posted so far.
I'll add to it a bit here, since I wound up rebuilding my entire instrument cluster not too long ago (I had some of the same issues).
A couple things to keep in mind here:
-Get a factory manual. Seriously.
-The dimmer switch acts as a sort of distribution point for a LOT of things behind the dash, including running lights, dash lights, interior, etc.
More than you'd expect. Trust me.
-The dimmers on these cars are notoriously bad and prone to failure. The gentleman on eBay who offers rebuilt ones may be a tad pricy, but his work is impeccable and comes with a warranty. The piece not only is better than new functionally, but appearance-wise as well.
-If your taillights AND dash lights don't work, that would point to a fuse, since they're on the same one.
Factory did that so that you'd know behind the wheel if your taillights worked by if your dash lights do.
-Don't forget the voltage limiter for the instrument cluster - it's that little silver box installed on the backside of the cluster. It knocks 12V down to 5V for your cluster and yes, the lights and gauges all get power from it.
Sounds like in this case your gauges ALL work?
Probably not the limiter then.
-Did I mention to get a factory service manual?
Invaluable when sorting out wiring issues on these cars - which I've just done on mine within the last couple years.
ALL the wiring. Every damn bit, as it turned out.

Good luck!
PS - I have an entire thread on troubleshooting this on here somewhere....