To my knowledge there is no way to hard wire a Ipod to a stock xterra radio . I have an aftermarket Alpine radio with RCA cable inputs. I went from a 1/8 inch minijack to rca connector to hardwire mine I also used the 12volt ipod holder in the stock location of my 02 x. If you have an SE with the fosgate radio you can buy a rca input adaptor from
www.crutchfield.com to hardwire.