Ideally you'll want something out of the '05+ models. I've tried some of the newest ones and found some of them to be incompatible with the e46 models. Some software wise and some of the newer ones don't plug in to the factory harness 100%. Best to look for one from '05 non-m or '05-'06 M3 and make sure it has the bluetooth symbol on the sticker. As for Pass Key, I've seen Bluetooth units with a Pass Key Number designation and ones without.
If you have something like a PA Scanner, you can enable BT yourself if needed in addition to changing the BT Name and Pass code.