v8sc400

i recently just bought a 92 SC400 and currently my car don't have cd player. if i want to install the nakamichi cd changer, what parts are require? for example, since my head unit don't have CD button, do i have to replace that too? how about the harness that connect to the nakamichi 12 disc changer? and i thought that all the SC400 comes with factory disc changer, many i was wrong. thanks in advance......