Anyone got any experience with repairing this model ?

Can't seem to remove the selector knob on the side.

Work was throwing it out as it would no longer drill holes with hammer, so I have stripped it down and found the pinion is shredded.

I want to disassemble it and throw it in the parts washer and clean it up and regrease it, but can't get this bloody knob off...

I have the IPL, but it doesn't really help with repair instructions.

Thanks fellas.