The M47 manual transmission on my '88 244 is giving me hell.

Not only is it notchy, but sometimes I actually can't shift it from 3rd into 4th the first time I try. It feels like the shifter has hit something that's
blocking it from going into gear, and then I immediately try again and it works. (When it's below freezing outside, it's also very hard to shift into
1st until the car warms up, but I suspect that's just the way it is.) I also get a clicking sound from the reverse-lockout collar whenever I shift into any
gear. And shifting into reverse, I often hear a loud clunk.

My mechanic looked at it a while back just for the notchiness (before I started having problems getting into gear at all). He there's enough fluid and that changing it probably won't do anything. He was reluctant to do anything and said the notchiness wasn't really a problem. But now it's gotten worse.

Thanks a lot for any help!

John--'88 244 DL, 107K, M47