Standard transmission

Hey all
Am having a shifting problem and am hoping it is only a simple adjustment. I have 300k on car and I don't think trans was adjusted at all.
Lately it has been hard to shift and when I push clutch in it at times it grinds a bit
Some times it hangs up in 5th gear to where I need to turn off and then I can shift.How long does the cable last on a manual trans and is it maybe just needs to be adjusted or quite possible needs cable replaced.
Am using a company car for now since I don't want to get stranded at the wrong time and I still need to fix the thermostat housing since when they changed it dang thing still leaks.
Is the cable easy to replace if that is what it is,or do I need to have a garage do it? All help from anyone helps me out. I am also contemplating buying another car and work on this at my leisure,when I can find a place that I can do it at

Ron 99 VW Jetta TDI 1.9 5 speed

Here is a good video showing how to adjust the linkage. It the course of doing this you will be able to tell if it's a wear or adjustment type of issue. Worth trying, but really I think if it were that then it would be equally picky whether the car was on or off.
https://www.youtube.com/watch?v=sheTKD03hmo

Is the clutch original?
Chances are good that you are headed for a clutch replacement.

How long has it been since the gear oil has been changed?

Been awhile since gear oil was changed.But you are right it might be clutch time. Have been doing a lot of in town driving and stop n go n stop Maybe get another clutch cable to be safe. Am going to get all parts before I put car in shop and let them do the job

No clutch "cable", it is hydraulic using the brake fluid.
It has a slave cylinder that can leak past the seals and/or need to be bled when the brake fluid gets changed.