transmission probs?

I have a manual trans. '85 s10 p/u and when i bought it, it had a high pitched sortof whining noise about it and as i've driven it over the last few months its gone from whining to shuddering and squeeling like theres friction or something .. it starts at about 20/25 rpms and gets real bad by 30 .. if i change gears at low rpms and don't go faster than 40mph its not so loud in 4th gear but whats this all about? I was thinking maybe it needs tranny fluid but how do i tell if thats it? there's no dipstick or fill place under the hood so what do i do?
-Steph

on the side of the transmission ,,,there should be a pipe plug,,,of some sort,,,,remove the plug oil should run out,,,,,if not,,, add until it does....
I like a blend of ATF and 30w,,,,,,only problem will be if you have been running this thing low on oil ,,,,,,probably going to need A LOT MORE than just oil!!!!!