Installing Stereo on 2001 Mazda Protege?

I want to remove the stock stereo and install an iPod docking stereo http://www.crutchfield.com/p_070XML8110/Dual-XML8110.html?tp=5684

According to Crutchfield, the unit fits but on the instructions they mention either soldering or splicing the existing connections and using a mounting kit. They include instructions and the harness along with the mounting kit for $130. My question is, will I really need to mess with the wiring or can I just use the existing connection and plug it straight into the new stereo? I ask because I can get the actual stereo for a little cheaper and buy the mounting kit separately. Are their packages really worth it?