Quoted:
you have a pre 07 diesel, highly desired around these parts.
Yup. Not only that, a 2006 with appr 30k miles. Very rare to find with all the options. Yours should be paid off, which means they want to get you for a new truck (and all the financing etc...) while paying a pittance ($10k-$20k) for yours, then turn around and sell yours for $35k0-ish (blue book is $31k):
here is the closest truck in autotrader... notice that this is the cheapest one... they only go up in price from here... 30k-45k miles.
Here is the same thing with 186k miles going for $20k. For $2k less than blue book, you could get this truck
here: 3 years newer, same generation, twice as many miles (35k more, 70k total). Stick with what you got.
You have a rare truck still under warranty. You've purchased new from them in the past. Your truck is most likely paid off. Why wouldn't they offer to buy it? It's an easy $20k minimum profit.