I am new to the forum, and read many interesting posts that have applied to many of my old chevy's. I am considering putting a nav unit in my wifes 2006 trailblazer. It is the bare bones model, no onstar, no bose. There are several units on ebay, what part number should I be looking for. In additon, has anyone performed this upgrade, and did that have any functional issues. I have read the tahoe forum and do I need to deal with the chime,volume, and VSS issues that others seem to have dealt with. Any comments would be helpful. Thanks