I though all E46 had CD changer pre-wiring, though perhaps that is only in the USA. Make sure you don't have the changer cables wrapped up in a bundle of fuzzy tape. Any of the E46 CD changer installation instructions on the web should have pictures.

The master junction for the iBus (as well as other circuits) is in the glove box by the fuse box. You can find instructions starting on Page 11 of http://web.archive.org/web/200701091...tion_Guide.pdf.

You can also find the iBus signal in the connector for the phone and on the NAV computer in the trunk. It should be white with red and yellow stripes.