I'm a bit new here(actually, this is my first post), but are you getting the faulty taillight warning lamp on the gauge cluster? If not you may want to check the taillamp warning module. Unfortunately it's in kind of a painful place to get to; it's underneath the interior trim panel next to the left side rear seat(driver's side if you're in the US). It's possible that water intrusion from a leaky rear quarter window can corrode it.
For fuses, you should have a fuse box under the driver's kick panel(it's a little back there; you might need a flashlight to see it), or under the hood near the battery. It's been a while since I've really gone through my fuses but I believe the taillight fuse should be under the kick panel. I have an '88 so YMMV.
-1988 Celica GT-Four(ST165): 47K, Weekend Warrior
-1988 Supra Turbo(MA70): 160K, Project Status
-1999 Lexus LS400(UCF20): 201K, Daily Runner