Estimated gallon use on-line?
 

Is there a map application (with features similar to Google maps, Yahoo maps, etc.) that will let me input both my route and my make/model/yr and then estimate how many gallons that I'll use?

I've never seen one, and probably wouldn't bother to use it if I did. Use any convenient mapping program to get mileage, then divide by whatever mpg your vehicle gets (28.5 from the data you have posted) to get gallons. Then multiply by a guess at gas price to get the important number, which is how much it will cost you. I think some Garmin GPS units have an inbuilt program which will do it for you, after you input your vehicle characteristics (city and highway mileage) and your destination. And the gas price, of course. They will even tell you how much evil carbon you emit.

I hope I didn't seem too abrupt. One of the problems such a program, or "app" if you prefer, would have is that it would not have access to whatever fuel mileage you actually get. If you enter a vehicle make, model, year, and even VIN, all the program could do is access some official fuel mileage estimates. Consensus seems to be that all those official estimates are incorrect in some degree - usually optimistic. When calculating mileage, almost all the mapping programs will do their best to route you via Interstate highways, even though there are often shorter routes. I had a GPS route me on a sort-of local trip, with the distance called out as 106 miles. The way I went, not via the Interstate, was 86 miles.