87 Trooper - Clutch Problem (I think)

Help,

I bought an 87 Trooper II about three weeks ago, after a full tune up, oil change and filters changed all was going well. Until last night.

Now it won't shift, it will go into like fourth gear only. Was able to get it into 2nd but I think I have a clutch problem.

I can work on things but am not good at troubleshooting. What should I check??

thanks,

Tony