manual tranny problems...

ok, the problem with my tranny is that it used to make a noise in reverse, now i wont shift at all, it locks,(the car wont move) the shiter gets stuck it only moves when i push the car forward, all the other gears work fine, but the speedo is bouncing and the check engine light comes on…:frowning:
what could be the problem? do i need another tranny or is it fixable? and why does the check engine light comes on??? please help!!!:frowning:

i appreciate any help!!!