If you are really a college student, you're probably on a budget. That said, unless you rely on your laptop for business (which you don't, because you're in college), a mechanical/non-SSD hard drive is fine. While HDD may not compare to SSD in terms of speed, with modern OS like Lion, HDD are very usable and still quite fast IMO. Plus, you are probably going to be more concerned with Gb/$, which you won't get from an SSD.
You can use optibay if you want for a HDD+SSD, but I would think you're better off just getting the HDD. If you can afford it and REALLY need the SSD, buy it but be prepared to have a large external for your movies and other large media since you won't have space on the SSD, and for TimeMachine backups.