Only real reason I can think of for legitimately changing the odometer reading is if you've fitted a different instrument panel/ECU which is showing a different mileage to the true one. With an electronic one though, you're looking at connecting the ECU to a laptop with the appropriate software to reprogram it. So take it to a main dealer for that make of car, who will have the software.
It's not illegal to change the mileage shown (eg to match on a replacement instrument panel)- but it is illegal to change it to increase the value of the vehicle or some other fraudulant reason.
Those of us who own and deal with cars with mileages well in excess of
100,000 miles really don't care what it says anyway!Rich.