It would just be a case of wiring it up.
Most here, however, would recommend the C5 Alive wiring kit, which gives you the option to use a wider range of batteries and apparently is more reliable too.
My personal C5 uses the original key switch assembly which I have never experienced a problem with. Having said that though, my C5 had seen virtually no use before I got it so the keyswitch may not have had time to start breaking down.