can i add a facory CD changer to my Factory head unit?

I have a 2002 discovery SD with a factory tape deck with steering wheel controls. There's a "CD" button on the tape deck but i don't have a CD changer. If i buy one of the "plug n play" CD changers on ebay that say they will plug directly into the factory harness, will that work with my steering wheel controls and head unit? I'm not sure what the factory plug looks like. Any tips on finding it?

thanks!

Ry

Have a look under your passenger seat. That is where the CD change is installed in my D1. The plugs for it are a small, white power plug and a larger, black (15 pin?) plug that has all the control and audio signals in it.