Bryan,
Probably broke a shifter pin. It's eay to check. Especially if you already have the motor out. Take off the plate that is on top of the suspect diamond shifter. Remove the linkage attached to the diamond shifter. The shifter then should lift out of the case. You may need to pry it out but be careful not to damage the aluminum case. On the other side of the sifter there is a plunger with an oring (or two can't remember). At the bottom of the plunger there is a pin that actuates the transmission F - N - R on that side. This pin will sometimes wear out or break. Some people replace the pin or replace the shifter as they aren't too expensive. Replace the orings and reinstall the shifter. This may not be the issue but its easy to check fix first before going into the T20.
Good luck, welcome to the sport and let us know how you make out.
Mike
"Don't worry my Dad's a TV repairman, he has an excellent set of tools..I can fix It"