Your contacts from the phone should still go to GMail, even if you didn't consciously do it. Its all done in the background. If you're able to download apps from the Market, that already means your phone has been associated with your GMail account.
Go to your PC browser and check your GMail account. Go to Contacts. You can check if everything is there.
If everything is there, give the phone some break period, after which, enter your GMail login and address again.