I think you're in the clear. The milage is stored in two different modules, which must agree. If you replace either, it must be reprogrammed by the dealer (or an indie with a $3500 computer) before the engine will start. The visible odometer only reports what the two modules are telling it. Must have been a clerical error - why would anyone go to that much trouble for 3K miles?

Buy it - you'll like it!