Help my new G54 is stuck

[85Flatty]

Here's the deal: I have a stock 1985 xtracab w/22r carb 4x4 flatbed. My head gasket blew and my tranny was leaking oil like crazy. So I decided it was time for some upgrades. I ordered a Marlin G54HD and got new gaskets from LC Engineering. I had the head bowl blended and had new valves put in. The G54HD came in first so I installed it, no problem(also put in a 1400lb clutch). I then proceeded to the head and while clearancing the valves my buddy checked to make sure the tranny was in neutral. He ran it through the gears and the transmission got stuck. Now I can't get it into neutral, I can't finish the valves and i can't figure out what to do. I have tried rocking the truck back and forth but this doesn't seem to help kick it out of gear. This all happened tonight and Marlin is closed. I really could use some advice on this one. Note: This is my first build and I am just learning. 

[79coyotefrg]

pull the shift boot  and shifter,  it sounds like it got crammed into one gear befor it was out of the other,   kinda sucks but it happens,  take a BIG screw driver and line all 3 forks up,

  never mind  we're talking a G54,  you'll have to remove the rear part of the tranny,  and slap your friend good for jamming the forks

[85Flatty]

Yeah, I also tried the big screw driver thing, it just cracked the dust cover flange

So, I have to take apart the tranny to fix it???