Before you condemn the gearbox, lift the transmission tunnel carpet & underfelt on the drivers side, remove the large round rubber gasket and shine a torch in the hole. (access to reverse light switch)
You should now be able to see the vertical selector finger which locates in the selector slots on the gear box. This is attached to the gear lever by a rod running through a cast Ali extension housing.
Anyway - what you are looking for is to see that the bottom end of the finger fits snugly in the selector slot - if it has loads of space around it then the bush has dropped off and the excessive slack will allow it to sit in between gears, especially if there is slop from wear at the gearlever end as well. My 2000TC did this and I made a new bush from a screwdriver handle (on the lathe, problem solved ). Alternatively the entire finger is available from J R Wadham. You can replace this item without removing the gearbox but will need to remove the gearlever, mid section of the exhaust and the propshaft, release the front engine tie and tilt the engine as far back as it will go - watch the fan & radiator. Then you can undo the 4 bolts holding the extension casting as there is now "loads !" of room under the transmission tunnel.
To turn the propshaft to undo the bolts (only at the diff end it simply slides out of the gearbox end), if jammed in gear - remove the spark plugs, make sure one rear wheel is free to turn and turn the engine with a socket on the crankshaft pulley (In this case get the radiator out of there or it'll cost £90 to have it re cored when you slip ! ). Good luck , dont fancy that auto box idea much...
