Chief , thanks for the props.

Scott,
I'm San Diego/ too far away to really help you.

Could also be the shift linkage is worn out or maybe just out of adjustment?
The bushings in the shifter tabs that the shift rods connect to eventually wear out and the shifter will not coordinate properly/ will hang up in or between 1st & 2nd gear.
A person can get under the car (raised safely ) & lightly tap on the trans lever tabs to get the trans & shifter back to a neutral state.

If it is wear on the shifter's selector lever pin & slots that has to be addressed by removing the shifter from the car and performing an overhaul on it.
If there are no replacement parts or replacement shifter available the worn areas can be built up by carefully building them up by welding ( use mig or tig process or gas weld there. NOT STICK) and the carefully grinding the slots & pin back to original size.
Just bear in mind that welding on tempered or hardened parts changes the metallurgy and to get good wear from the weld repair the piece should be re heat treated or re- tempered.
I've had to do this before with some cheap aftermarket shifters (SparkOmatic comes to mind) when there was no other way to effect a repair.
Best to get all the wear & slop out of the shifter & linkage before adjusting the travel length on the rods

I can send you the factory adjustment procedure for manual trans floor shifter if that will help out. I think I have it lying around hear some where.
PM me and I'll email you the info.

Other thing I have seen happen is the one of the stands for the release fingers on the pressure plate/clutch cover has broken and the clutch will not fully release when the pedal is pushed in (Borg & Beck style) . The trans will be stuck in gear. Broken / missing segments on a diaphragm spring type clutch cover will also cause the same problem. Only fix is to pull the trans, remove the clutch disc and pressure plate assembly and check for damage.

If you are getting full pedal travel and can actually see the clutch throw out bearing lever moving the clutch linkage should be OK.
Hope that helps you & your mechanic trouble shoot the problem.