2005 Nissan Sentra stereo wiring

Anyone what wire on a stock radio in a Sentra, I can use for the radio mute installing a Motorola HF 850kit, if not can I use a relay, and interrupt the power going to the radio. I think the Motorola mute wire is a neg, so I would need a relay, and just use the mute wire for the neg of the relay. I think that's the way to do it, any help would be appreciated.