I've got a 1995 Diesel GMC Suburban. Best truck i've ever owned (and I've had them all). I would buy another right now if they still made them. I would never own a pickup again, but if that is what you are in the market for then get a diesel one. More specifically go GMC/Chevy (The Cummins in Dodge trucks is a great engine, but the trucks themselves are terrible, and the new Ford diesel is junk). Diesel really is great, especially in a full sized truck, I get 22mpg highway (compared to about 10mpg in a similer gas truck) and could tow almost twice as much. Oh, and Diesel is more efficient than gas, whoever told you otherwise is completely wrong.

As to there being less diesel then gas. Fuel oil used to heat houses is just dyed diesel. It is illegal to use it in your truck, but in an emergency you could use it as long as you don't get caught. Gas pumps may be empty, but you can always find diesel somewhere. Especially by a highway. Also, in 2006 all diesel is the states has to be low sulfer diesel like in Europe, so you will start seeing a lot more diesel pumps and diesel vehicles.