Locked into second gear

Greetings!
About 3-4 weeks ago while driving home I shifted from third to second
gear and the gear shift immediately went, for want of a better word,
limp. No grinding, no lurch, it just went into second and won't come
out. The clutch will depress and apperas to be operative, but the gear
shifter does not seem to be linked to anything anymore. This is a 1996
SL1 sedan, with about 100,000 miles on it. I've been told by various
people over the phone it could be anything from a stripped gear, to a
bad transmission, to just needing clutch fluid. Unfortunately, I can't
locate the clutch fluid dipstick, so if anyone could point me to that,
I'd appreciate it. Any ideas/comments as to what maybe wrong?