As a resident, all you need is a limited license. However, certain programs like mine encourage residents to apply for their full license before they can do moonlighting shifts. The full license is much more of a pain, requiring plenty of paperwork, which may or may not get screwed up by your internship people as they're filling out the forms for you. Once you're done with internship, I'd recommend you jump on getting the full license so you have less headaches in the end. (that said, if you're leaving the state after your residency, you'll end up jumping through all these hoops once again for your new practice).
chris