There is a trailer there that has been staffed at times but I don't know if they sell tickets inside. I've seen people go in though. Megabus tickets have to be purchased online.
Multiple busses stop there, you might have to go online and see what busses you could get tickets for and see if an email will suffice as a ticket, some buses required printed tickets. Wouldn't hurt to ask on the bus though if they're the same company as the bus you're expecting
Thanks! Your answer is awaiting moderation.