Most manual transmission shifting problems aren't with the transmission itself, but more often with a clutch, flywheel or clutch master cylinder.
Bad pressure plates and time cause flywheels to warp. Resurfacing insures the longest life for your new clutch.
If you do need a new clutch, the pressure plate will also need replacing. Conversely, if you need a new pressure plate, it makes the most sense to replace the clutch too because they work together to disengage the transmission to allow shifting. The labor to replace these components is more that the cost of the parts. You wouldn't want to do one only to have the other fail soon after the repair.
After a clutch/pressure plate/and/or flywheel resurfacing, you will be able to enjoy the vehicle performance you may have long ago forgotten.