How do I fix my shifting problem that I stupidly created?

I have a 1989 Chevy C1500 manual 4 wheel drive. The shifting worked perfectly until I got stuck in deep snow and rocked truck back and forth aggressively by shifting from 1st to reverse and back again. I also went in and out of 4 wheel drive- both high and low aggressively. The truck stopped moving after doing this a bunch of times. Fast forward 5 months - warm weather now - and I can get it to move forward and reverse in 4 wheel low and in 2 wheel drive. But, the performance is erratic and I need to almost floor accelerator. What can I do to fix it?