Manual Transmission - 4th gear stuck!!! HELP

I was driving home from work, shifting normally, not abusively. Suddenly could not get shifter out of 4th gear. I tried pumping clutch, even turned off motor. Finally, brute strength pushed out shifter. Car drove home fine after that.
this past weekend, just did a fluid change (4 qts Dex 3 ) and added B&M Ripper Shifter.
Im stunned...any ideas or is this a tell tale sign of worse to come.
thanks

Sounds like the dreaded broken syncro slider keys.
If it is a rebuild is in your future :(

Yep, good ole stock stamped slider keys. I had this happen to me. The first 3 or so times I was able to get it out. Then, one night, it was there for good. I had to drive it home in 4th running stop signs and everything. I tore it apart to find the slider all broken in the syncro. Billet sliders and some other parts later, and she was better than ever.

is that an easy fix? Is it best to get it done soon or the same outcome no matter what?
how would you go about doing the repair, including good parts?
thanks

Basically remove & completely disassemble the transmission to replace the 3/4 keys.
Might as well rebuild it while your there IMO.

I am able to do the removal and reinstall of the physical trans myself, but $ wise, to have it rebuilt, what's the approximate rate?
Do you think the shifting problem will go hand in hand as to how hard the car is shifted?
I try to drive nicely...helpfully I can get quite a few more thousand miles out of it, the car has 84K. I just have one grudge race at the end of the month, other than that, its a "fast" daily driver.

I would drop that race and get it rebuilt ASAP before you damage even more things. Try t56rebuilds.com they are a sponsor here. Probably rebuilt would be 1000-1200 range if you are doing install/removal yourself.