3rd Gear Grinding?!?!

I purchased a 95 Integra LS in Mid-January and about a month and a half ago 3rd gear started grinding whenever I shifted into it. I heard it was a common problem with LS transmissions. What should I do? Buy a whole new 3rd gear from the dealership and replace the one I have, or buy a new transmission with lower milage and have that installed? I do not have a lot of money to spend on this either, if anyone has any suggestions or advice, please respond, I would appreciate it. Thanks