164 gearbox internals

My 24v box is stuck in 2nd (or first, but I think second), the gear selector shaft is moving in neutral between 3/4 and 5/R. How can I access the 1st/2nd shaft to push it into neutral? If I take the gear selector shaft and its bushings out, could I get something in to do it? If I take out the 3 spring loaded ball bearings that provide positive engagements for the rod's three positions (e.g. 1st/neutral/2nd), will I be able to move it from there? Or would I have to get at it by removing the end cover? The 5th / R shaft is the long one and definitely sticks out into the end cover, but I can't work out if the other two are accessible from there.
Sorry, I'm not up to speed on gearboxes, but I'm learning fast!