Newbish project - Hopefully simple 360 controller mod

[electricmulch]

I have an XNA project I'm trying to work out but it has an issue due to no support of accessing the microphone input.

So what I'd like to do is take a cheap/used controller and wire it to one of the axis of one of the analog sticks preferably with some kind of toggle switch between the two inputs. If it wouldn't be too difficult/unsafe to do so, I would like to yank the combo mic/headphone jack and replace that with a normal, mini headphone jack instead.

Any obvious pitfalls/suggestions?