[PSI240SX]

I purchased a 1995 240sx that has been sitting underneath a tree for about 4 years now. I talked to the last person who drove it and they said everything worked properly when it was parked. Besides the live rats living in the engine compartment, it looks really nice after the first cleanup. Much to my surprise after putting a jump box on it it fired right up. I turned it off immediately so that I could change the fluids before really running the car. Changed the fluids, and poured in some fresh gas and started it, letting it run for a few minutes and get up to temperature, the AC works and all of the guages except for the gas guage. I went to move it out for a test drive and it wouldnt go anywhere when I let out on the clutch. Since the throttle cable was frozen I figured maybe that the slave cyl. might be as well, but I checked it and it moves back and forth just like its suposed to. After trying more gears I got it to move slightly in reverse, but it wont go anywhere now except in 4th gear. Any idea's? The slave moves just as it's supposed to so I suppose I will have to try and pull the tranny, but what should I look for?
Thanks in advance for your help.