ECM Relacement on 2000 Z24

I damaged my ECM by boosting another car. Now my mileage reads 888888. A auto electric shop said to put in another ECM unit since that is where the milage data comes from.
I assume a new one would have to be set up at the dealers. Since I can't afford a new one this won't be an issue.

Instead several auto wreckers say the can sell me a used ECM that will work perfectly in my car, about $80.00.

Are the wreckers correct and what will the mileage read? The mileage of the Cav the unit came from.....or? Also, how similar do the two cars have to be for the used ECM to work properly.

By the way the car runs fine other than the odometer reading.

Thanks in advance

I would go to the Dealer first, the electric shop is wrong I bet. Although the PCM stores the mileage in some applications these cars use what is known as a smart cluster and since your car runs fine I seriously doubt you fried the PCM you probably brained the cluster. Try disconnecting the battery and see if it starts to work. E-mail me if you have any questions.