The 9mm +P rounds outperform standard 38 Super. Seems like a lot of work for a marginal improvement in velocity with a 38 Super +P. Now if you would consider the 357 SIG I could see the point.
Technically all 38 super is +P. You'd loose a round going to the 357 sig and not gain near the velocity over the super as he would going from 9mm to 38 super.
As to the op. cutting the chamber and changing mags is all that's needed the extractor will work fine as the rims are nearly the same size. you may want to have it cut for 9X23 though.