Merge is stored in the cluster, so it would need to be reprogrammed. You'd probably have to go to the dealer with your stock cluster in the truck to show actual mileage, swap clusters, and then have it programmed.
Good luck getting a dealership to reprogram the miles for you. 99% of dealers will NOT reprogram it unless it's a new cluster with zero miles. I bought a Denali cluster with zero miles and plugged it up to test it out in my truck. Drove it for about 6-7 miles to get the trans up to temp to verify that the trans temp gauge was working. Then I go to get the miles programmed and every dealer in town here refused to do it because I had 7 miles on the cluster. I was like AYFKM??
Ended up selling the dam thing for what I paid for it because getting it programmed was too much of a hassle. I did end up getting another one a year later in a trade, and it's sitting in my closet STILL waiting to be programmed.
God I wish I had a Tech-2 and I would just do it myself!