It's a surgery, and has a recovery time, yes it's going to hurt. It will leave a scar, but, being where it is... You'll never notice once it's healed and neither will she! Once it's healed, your risk of urinary tract infections and just generalized skin infections "down there" will be reduced!
You just made me break out in a sweat!!!!
I'm still amazed about what can be found on the internet:
http://www.circinfo.net/men_circumcised_as_adults_tell_it_as_it_is.html
I've had surgery in that area. Kinda. Sorta. Well, close. Yes, it can be a little painful but they'll give you pain killers.
Of course, I'm assuming you're getting it done by a surgeon and not by some witch doctor. If that's the case, go read Ancient Hippy's answer again.