I'd check the clutch adjustment for the tranny grinding. The clutch adjustment is easy. See the manual.

The shift rails are right above the gears for sure, but the gears have nothing to do with shift quality in the tranny unless they interfere with the shift railsm and I don't believe that would happen unless the tcase grenaded.

I can't guarantee that nothing is wrong with the tranny, but I don't think there is a lot wrong besides clutch engagement. I base this on the following. All the gears have crunch, worse on downshift. Thus just one syncro is not bad, all of them would have to be, or the shaft bearings would have to be very bad and the tranny would be very whiny/noisy.

And you don't need a new carb...