Speedo is wrong

I had to have the speedo replaced in my 2002 Quadrasteer. Yes, this is the one that went under water for a few days. I had 19000 miles on the truck and the replacement speedo I got from the junk yard has 156,000 miles on it. The dealer say's it cannot be reprogramed. What do they do when they change one? They can't go back to zero with a new one. I have given the truck to a young friend and would like to take care of this problem for him.
Thank's
Jim.

I thought there was a decal that had to be applied to the door jam stating what the current mileage is on the actual vehicle and what the "new" odometer reading is at the time of the swap......correct me if I'm wrong though...

No it cannot be programmed by the dealer but they can have it set for a fee by an authorized ACDelco cluster and radio repair center.

I'll look into having that done. The sticker is OK, but I don't like the idea of the reading being so far off. Looks bad.
Thanks for the reply.

Guys, a guy in Mexico reprograms them, though you just can´t pass a cluster through customs though....