I did as well, though I can't find the change/port link the e-mail refers to. Sooo, I can't do it.
Hmm... well I went with "option 2" and made my GV number my sprint number and that seemed to go through ok. I tested calling and text messages and they both showed my GV number. Also, now my cell number on the GV page says "google voice enabled."
One thing I found interesting with option 1. Now, all my text messages default to the Google Voice app instead of Handcent SMS. They aren't picked up by Handcent at all.
So, I'm trying to find a way for Handcent to still receive the SMS messages. No luck yet.