car won't go in any gear?? Fluid is full and cable is still working the trans...

How would I go about testing? Does it need a new fly wheel or a transmission?

Check the transmission fluid level with the engine OFF ... Then check it again with the engine RUNNING .. IF the fluid level does NOT change (go down) ... The TORQUE CONVERTER is not turning the internal transmission fluid pump shaft due to stripped out splines inside of the converter hub .. Transmission removal and inspection is required .. Most of the time, replacement of the 'torque converter' and pump shaft is all that's needed..