So you have a developer account already?
That was not clear.
I've not worked with anyone else as you are (I'm my own developer) so I'm not sure of the steps.
I think you're on the right track though
Whatever you do, do not give your iTunes login credentials to the developer (or anyone else for that matter).
Oops, I did give the developer my login info, however have since changed the password. My app is now being reviewed however I received some email saying I need to do some changes on something about an API. Guess, I'll have to do some research and ask a lot of questions to get it taken care of.
Thanks for your input.