Problem going into any gear

[pov02]

I've just recently rebuilt my engine and transmission (by TRE) and now i've ran into a problem. The good news is the car starts . But once i've tried to take it for a joy ride, i found that the car won't go into gear??? I've bled the clutch and bought a new slave cylinder and everything. I've tried to put the transmission in gear manually (moving the shifter arms on the tranny by hand) and it seems to go into gear pretty decent. I've even tried to adjust the shifter cables (don't know if its necessary). After weeks of thinking about the problem, i came to two conclusions. First conclusion is maybe my brother and i installed the clutch in backwards (because we did once in the past; therefore, we double checked the clutch disk this time to see if its in right before putting on the pressure plate). Or second, maybe i've placed the little spring inside the clutch slave cylinder backwards (due to idiotic cousin who decides to press the slave rod in when the slave cylinder is off the tranny; by doing so, the little spring blasted its way into his eye.) I haven't tried to tear the tranny off the engine yet to see if the clutch is backwards or if the spring is backwards because i haven't got time, but in the mean time, please reply back if you know what the problem might be or if you encounter this before. Thanks