I'm new here, this is my first post, so I hope you'll forgive me any faux-pas.

I've been looking for a car to replace my tempermental Volkswagen and I recently saw a decent looking 80-something 740 (non-turbo) sedan for $500. The car has no rust to speak of, only 109k miles, and a 4-speed manual transmission with pushbutton OD. I forgot to check but I would guess the car to be mid-eighties vintage. The car had a flat tire and was frozen to the ground when I saw it, so I couldn't test drive it, but I could start it up and the engine ran well. I did press the clutch a few times and it felt a little wierd, the pedal action felt kind of stiff, getting a little stiffer the lower you pressed it. Should I assume that the clutch is bad, or could this be something more simple, maybe just the clutch-cable? (my minimal research, so far, has told me that this car should have just a manual cable-operatd clutch, no hydrolics) I figure, though, that for $500 if the rest of the car is good I can afford to replace a clutch if it does turn out to be bad.

The question I was really hoping to get answered here was whether the 4-speed transmission (from my minimal research I have done I can assume it's an M-46 transmission) has a good reputation for durability. The presence of the overdrive worries me a little, in my experience features like this can often end up being more of a hassle than they're worth. Assuming that it's in good condition now, could I trust this transmission over the long-term? Would it need regular maintnance? Filter changes? Fluid changes?
Is there anything else I should keep in mind if I go to take a second look at it?

I thank you folks for any help you can give me.

-Jason