I did a singing course on the weekend - I am absoloute beginner, but it was fun and I think it did definitely work better for me than pre-OP. I could hit the higher notes more easily, but I did have trouble around my voice break, which was not so pleasant. The interesting thing is that the other women in the course had often trouble reaching the C5 but for me that was not a problem, I did have a large vocal range pre-OP as well, though. What I did notice however was that the course was a real strain on my voice and I rested my voice for a day after that because it was feeleing strained.
Amy_Berlin is a professional singer here who had the Yeson surgery. She does record CDs with a band she is in, so there are probably recordings available. Also J-Mie (you can find her on youtube I think in the context of rave music as J-Mie and Mi-Di IIRC) had the prcedure and does recordings. I think the ones Dr Kim mentioned there are Korean singers though. I know he did the surgery on a transgender pop band from Korea.