I'm looking to update the Nav DVD in my RX 300. Is the "first DVD upgrade free" rule for all Lexus dealers? Is that documented anywhere? Since I bought mine from a person (not a dealer), it may be a challenge to get the dealer to honor that. If I can't get the free upgrade, is there somewhere people sell (or give away) the old disks? Mine is about 3 years old, so getting a year old disk is perfectly fine with me. Thanks for any help.