[Veselin Kolev]

Well, it looks like you don't want to use the .7 module gear on the motor, or the transmission that comes with it, so you can do a few things. Some more eccentric than others...

You can remove the pinion with an arbor press and press on a new gear
You can mill off the teeth (very difficult to do) and key the remains, and put something on it using the key.

Yea.. what most teams do is just use another .7 module gear to mesh with the drill motor's gear, and then attach another type of gear to that one. This makes life a lot easier. But there are also many teams that just press the gear off and put on a new one, so their entire transmission can use one gear type.