I just purchased a 2006 MDX and the Navigation system is broken. Dealer is telling me that the unit cost is 3K my question is are there a couple different units that work in this car or is the part number 3954-s3v-407, the one the dealer quoted me, the only one I can use in my car. I look out on ebay and there are a half dozen that say it is for a 2006 with very similar part numbers but the last 3 or 6 digits are different. Any help please would bew great!