Hello, I recently bought a factory DVD navigation system for my 2007 silverado ltz. The unit is in good condition but is from an 08 model. The dealer said they couldn't program to my truck because it was an 08. All it shows when plugged in is "theft lock". I really need some help with this! With some consulting I learned it was very possible to program it, the tech just has to know how to do it. Has anyone had a similar issue, if so can you help me?