Read a few of these articles/threads and see if they help.

From BT forum: LINK

From BT section: LINK ----------- LINK

So here's my take. You can install the BT/assist module from an 05' to work in your 04' with no problem. In order to have VR, you will need to install a separate VR module. You will already have power and car antenna accessability in your armrest.

Read these articles/links, and come back with any other questions.

Greg