My learners permite expired, can I just get it renewed or do I have to retest in MD?

My learners permit (for driving) expired on April 24th. I need to get a new one, but I'm not sure what to expect. Do I need to retest for it? Can I just renew it? Do I have to hold it for another 6 months? What fees should I expect? I'm in MD, and under 18 by the way.