I don't know if there is an easier way, but I would recommend just taking your iPhone to AT&T and asking them to back it up. They'll transfer all of them over to your Infuse at their store.
I tried to sort out the contacts on my mom's iPhone and it was horrendous. I don't know if I just didn't know an easy way to do it, but the back up options did not work well (iCloud, you can't tell/see, even though you're supposed to just believe it's all being back up there on Apple's servers) and the iTunes options for syncing the iPhone to GMail worked just as well as... well, not working.
Seriously, I have no idea why iPhones are supposed to be easy to use... I mean, maybe for more things, but boy, while I was helping my mother out with her phone, things like the contacts and not being able to download email files for mp3's and whatnot drove me crazy and made me believe Android is not necessarily any harder to use than iOS (if not easier... at least in my opinion, now).