How do we siphon gas contaminated with deisel from a 2001 Yukon Denali? Specifically, are there compartments or baffles within the gas tank that would prevent siphoning with a hose?

Dropping the tank and flushing is the best option. Those estimates are pretty good for that amount of work. You could look into a mobile mechanic, to save even more (you can find one on Craigslist). Option 2 is siphoning and diluting with good gas. Siphoning alone will never get all that contaminated gas/diesel out, but if you get most of it out, fill up with good gas, and add some high-octane gas treatment (for the next few fill-ups) your engine will survive. After all that is said and done, you'll need to replace the fuel filter and maybe run some engine cleaner through the engine as well.

Found this on the interwebs: http://blogs.tech-recipes.com/qmchenry/2006/10/13/what-to-do-if-you-get-diesel-fuel-in-your-gas-vehicle/

Siphoning fuel from modern cars is pretty much impossible. You may need to remove the tank or use the fuel pump to pump the fuel out. A small amount of diesel should not hurt anything.

How much diesel did you put in the tank?

Agree with Full of Regrets, how much diesel is in the tank? If it were 2 gallons or less I probably would fill the tank with gasoline and drive it. If there is more than a couple of gallons do some creative tinkering and use the vehicles fuel pump and pump it out. No need to flush the tank in this situation. Small amount of diesel won't hurt a thing.

A full five gallons. A horrible mistake involving using a gas can to store diesel and then forgetting. This model holds about 30. It already had about 5-8 gallons of regular gas in it. We got under neath and removed the hose from the mouth of the tank and were able to get about a gallon out with a common gas siphon but either the hose we are using is too thin, too short, or maybe it is looping on itself because we haven't been able to get any more out. That's why I wanted to know whether the fuel tank has internal compartments or valves or whether it is just one big open container. If the former, and we can't get to the rest of the deisel then the tank may have to come off. If the latter then we get a longer, thicker hose and try again. Thanks for all the help.

I believe there is an anti-siphoning device in the gas tank neck and there should be baffles in the tank itself.