Transmission dilemma

[neon]

I have a 1970 Chevy 4x4. This week, the transmission (I think something with the 'forks') decided to go out. I can shift into 1st and 2nd fine, but when I try to go over to 3rd, 4th, or Rev, it jams as I try to move the shift lever to the right in Neutral. I can 'wiggle' it around and get it over but it takes some real effort, and coersion. I pulled the seat out, cover off, and shift lever out of the transmission. I tried to pull the top cover off the transmission, and I can lift it about 1/2 an inch and it catches on someting and won't lift any higher. Has anyone ever experienced this dilemma, and if so, does anyone know what the cover may be catching on, and how to get it 'unstuck?'