Hi Eric, Tough questions to get answers to, heh?! Here's some general thoughts and observations for you to consider. Diesels hold a premium to their gas counterparts. As usual something that you pay a premium for, will therefore sell for a premium (assuming the new product isn't a lemon in design and/or engineering, which the EcoDiesel isn't). You get a diesel because you put high mileage on a vehicle and want the durability (diesel fuel has oil in it so it functions as a lubricant as well, and diesel engines don't have as complex of an ignition or fuel system), and the fuel efficiency. So most gas engines will go 100k easy nowadays. Most of mine I ran right around to 200k, and at that point some had valve seal leaks, oil ring blow by, basically just tired. I'd look at overall wear (seats shot?, paint faded? etc.) and many times couldn't justify getting the heads done when everything else looked worn out.
So if a diesel keeps chugging along, are you one that wants a new vehicle every 5-10 years? The 3D's also need to hit the open highway so it can burn off the particulates. I'm around town a lot dropping off kids at soccer running to Home Depot, but I'm usually on the highway at some point during the week for at least 15 minutes visiting job sites as a contractor. But once every 3-4 months or so, my regeneration message will come up, so I can live with this. However, if everything you do is within a couple of miles of home then I would not get an EcoDiesel.
Anyway, that's all that comes to mind now. Hope this helps.