With the horizontal shift rod (the one going forward to the shifter) disconnected and the shift coupler still attached to the shift rod going into the front of the transmission one should be able to go into all the gears (if all is well with the transmission) with the clutch pedal depressed. Use the shift coupler as a handle.
Detent plugs:
On passenger side: 2 with threaded plugs on side and lower down and one higher up (vertical hole with tap in force fit type plug - right under black wire in below image).
