Is this the piece I need? http://www.radioshack.com/product/index.jsp?productId=2062402&cp=&sr=1&origkw=Piezo&kw=piezo&parentPage=search

Im just making a cheap, easy one for my friends guitar, and want to know if this is the one to use, and is all you have to do is cut the rubber? off of it? Then hook up the wires to a jack and mount it? Which side goes up, teh ceramic or brass (I beleive its brass)

Thanks for your help.
Yes, that one works. That is a hard plastic shell around the piezo element. You need to break that away, being careful to not damage the element. Brass side down and the ceramic side exposed. I have gotten away just using silicone to hold it into place. Twisting the wires helps cut some interference.