Single rear exhaust exit to a dual exit?

Hey guys! This is my very first post in this forum and I am super excited to discuss the g6's

Quick question?

I have an 07 GT you know with the single rear exit, and I want to make it to a dual like the GTP's and GXP's and then possible get that GT-R exhaust kit.
If I take it to the shop do you think they would know how to cut the hole identical to the other one so that I could have dual exit now.
If so how much would it cost you think?

Thanks so much!