Front yard Shade-tree version....
Just did this with the new HL full bearing gear boxes, converted to a final driven taigen shaft (larger diameter sprocket interface):
split the gearbox (4 screws),
remove final driven shaft/gear,
I used a spring center punch too loosen the pin that holds the gear on the shaft, drove it out with "old" drill bit (now it's a drift). HL pin note: look for the side that has a chamfer this is the side you want to drive the pin from the other side is knurled. Taigen are knurled in the center.
Then using a 3/8 drive 13mm deep socket supporting the gear -drive (press, arbour, vice or hammer) the gear off the shaft.
Reverse process to assemble.
Found that one of the shafts wasn't drilled centered for the pin, so the pin didn't fully seat flush so it needed to be ground so not to interfere with the last drive gear.
Also I learned that clear plastic tubing (like the smoker) can replace any spacers on the shafts, HL uses this method -it actually puts a slight pre-load on the end play -great stuff, Taigen uses aluminium tubing.