Have you adjusted the tracking force properly? This likely wouldn't change the sound drastically, but since you said this is your first turntable I wanted to make sure you know to adjust it. Also, I'd recommend buying at least one new LP to serve as a benchmark for your turntable. It will allow you to eliminate the LP as any source of problems you have now or later on. By new I don't mean some LP that's 30 years old but happens to be unopened. I mean a new LP that was actually made in the last 10 years or so.
Do you know whether the stylus itself is clean? I don't know where you're located, but see if you can find a Mr. Clean eraser at your supermarket/grocery store. Moisten the white sponge side, and carefully dip the diamond tip into the sponge several times, but DON'T drag the diamond along the sponge. This sounds like a strange method to clean the diamond, but I saw it recommended by several guys really experienced with turntables, and after trying it myself it really works. The more traditional method is to wet a soft bristle toothbrush with Isopropyl alcohol and light brush the diamond.
As Peter said, you may need a new stylus, and the soundsmith smmc4 isn't cheap compared to the price you probably paid for your turntable. You can also watch ebay for another mmc-5, but the amount you'll save might not be worth it, as the soundsmith smmc4 would likely sound better.
Austin