Can't Shift gears

[88GT 5pt0]

After Driving my car for about 15-20 mins, it gets extreamly hard to move the shifter into gear. Any ideas what that could be

[Dark_5.0]

Either your synchros or your clutch or both are on the way out.

[USMC302]

When was the last time you changed your fliud?

[88GT 5pt0]

I was told that the fluid doesn't need to be changed on a manual trans and sounds like my clutch was out of alignment.

[USMC302]

I would suggest changing it every 80k or so. missing gears and such cause small metal flakes to build up in the fluid, cycling fluid with metal in it isn't esuring the longest life of your tranny ya know what I mean?