Gas milage and odometer GONE!

I have a question that will likely stump even the best wrench turner. I have a 1999 Ford F-150 with 61,000 miles and a 4.6 engine, 2 wheel drive. I got a letter from Ford that there was a saftey recall on the brake/cruise that could start a fire.
Now, I take VERY good care of this truck. At 61,000 miles it looks AND runs like it just came off the showroom floor. That is how good of care it gets.
I took it in to the local dealership to have the recal taken care of. At this time I was averaging between 22 and 25 MPG with in town or highway and could always see my odometer wich I look at religiously.
Upon getting it repaired and leaving the shop I had to go to work wich is 28 miles away. The first thing I saw after 2 miles was that my odometer was BLANK! Heading to work with not much time to spare I comtinued on and set the cruise to 65 MPH After the first 10 mile I looked at my fuel guage and found I had just used up a 1/4 tank of gas! By the time I got to the end of my 28 mile trip I had used just over a 1/2 of a tank! For 28 MILES?
I called the Ford dealership who told me to bring it in right away wich I did the next morning. They went through it from top to bottom and end to end and came up with the answer of the odometer from 98 to 03 just goes out and the whole dash cluster needs to be replaced, must have just been a coincidence. (Well, I can deal with that, for $478.00 "I guess") as for the gas milage "Don't know. Must just be one of those things." No leaks, no smells, did the battery disconnect thing and Diag. Computer says all ok.
So I need another educated guess of what may have happened or if I just need MY head exammend.