[olddog]

If it will not go into gear with the engine stopped, it is not the clutch.

Now a transmission in a stopped car with engine off, can be stopped at a place where the teeth are not aligned. You should be able to find at least one gear that it will easily slide into. You should be able to rock the car and align any gear so that you can easily shift into that gear. If you cannot do this, then the problem is in the transmission.

If you can shift into and out of a gear with the engine stopped, start the engine and now it will not go into gear, that is the clutch not releasing or TOB dragging.

If it is the clutch, put it into gear with engine off. Start the engine, with the clutch fully depressed. Now slowly let off on the clutch and see how far off the floor the pedal is when the car starts to move. If it is the clutch not releasing, the car will start to move with the pedal slightly off the floor. If the pedal is near half way up, it is not a clutch adjustment issue.