Changing the Shafts on a Toughbox Nano

[SciBorgs]

My team has to change the shafts from keyed to hex on a toughbox nano to fit new wheels. It is just a solid piece of channel, so we can't exactly open it. I assume it is possible, since the AndyMark page sells replacement gears and shafts, and I looked through the assembly guide, but I can't seem to find a replacement guide. Have any of you tried doing this, or something similar? If so, how much time did it take, and are there particular things I should do to make it easier, challenges I should expect, or tools that will make things go quicker? Thank you for your help.