97 gmc sonoma 4wd problem

hey, i have a 97 gmc sonoma 4.3 vortec and i cant get it into 4wd, today i went under the truck and saw that it was ran by a cable so i was thinking that its froze up. i cant seem to figure out how to get the shift knobs off so i can take the plastic cover and the boot off the shifter and the tcase shifter, i was wondering how to get that off and if theres anyone who has had a similar problem or if theres a write up on how to go about doing this, thanks keith