You may have already done your upgrade, but here is a synopsis of the things I found out while upgrading my 2004 vibe. Head to the last post in this topic to get my summary:
http://forums.genvibe.com/zerothread?id=41358You will need to buy a double-din adapter for your head unit - a place like crutchfield can give you good recommendations for the particular model you bought, etc.As noted in the topic I linked, you may need to cut some plastic off the adapter kit before it will work. Don't be shocked by this, it is designed to fit in a variety of vehicles, so just snap off what you don't need. The factory brackets did not work for me.