Possibility of editing the rebel uniform in HL2RP?

I want to add a mask to the Rebel uniform to make a uniform that is leader/ character specific. How would I be able to do this? What software would I need?

This is what I want the mask to look like.

jesus christ that image scared the shit out of me

>:D it’s a photoshopped variant of my halloween mask I made.

Oh wow I thought it was a screamer for a second.