You should be able to take it to a regular machine shop, but check they are good and make sure that the wheel is clocked up and runs true before you start machining. Whether you also have it balanced is up to you, i didn't because I trust the guy who did it and the wheel ran perefectly true before machining.
Runs great with no vibrations so must be ok!
At the same time I had som more removed from the back face to get rid of some more weight!