I'm not a turntable owner myself, however I've been doing a bit of research into them for the last month or so as I too am considering getting into vinyl.
Does your amp have phono inputs on the back? If not you'll need to buy a phono stage. Turntables put out very little voltage by themselves so the signal needs to be brought up to line level. Also phono stages provide the RIAA equalisation. Plenty of information on these topics can be found on the web.
I agree that it's risky laying down money for a format you're not familiar with, and therefore not sure you'll like. However, based on my reading, I'm not sure you'll get anything worthwhile for that kind of money, unless you go vintage (which has risks given the mechanical nature of turntables).
One of the most popular budget, but well respected, turntables seems to be the Rega RP1 - which go about $450. Perhaps you should try auditioning one to help make up your mind whether you want to invest in the format and get the most out of it.