2nd gen manual trans not going into any gears????!!!!

Hi all, new to this forum and this is my first post.

I bought a 87 power ram yesterday for $500, everything worked "well enough" to get it the 30 mile drive home. The previous owner said that the 4th gear synchro was bad and it was having trouble getting into 4th and staying there. When I test drove it and put it into 4 hi/low (has automatic wheel locks) it went into 4wd fine, but didn't completely come out apparently. When I got home I noticed that it was leaking thick black oil profusely out of the transfer case, a friend suggested that it didn't fully disengage from 4wd.

It seemed to shift fine though (better once it had warmed up), but today when I got off the freeway it was having a lot of difficulty popping into gear. after a few shifts it refused to go into any gear at all and just kind of remained in neutral. I got it to go towards reverse but couldn't get it in gear, just heard the gear mesh grinding but not engaging. Luckily if stopped right around the corner from work and I just pushed it the two block to the parking lot where it now sits.

Can anyone give me some insight as to what might have happened? I am a very mechanically inclined individual, but don't really know anything about working on cars, thats why I bought this old thing-to learn how to wrench.

Anything would be appreciated!

Is it grinding?
Do you feel the "detents" or any type of thing?
Many times the plastic cup / bushing falls apart in the shifter and they won't go into gear.
If it's grinding then the clutch needs to be adjusted.