I have a '98 Expedition with 223k miles on it and swapped the instrument panel because most of the lights in it were burnt out and the plastic cover looked like crap. So I replaced it with one that had 98k miles on it. everything worked great for about 10k miles then it just stopped counting miles. It's a pain to pull it all apart so I left it for another 2000 miles then I finally broke down and pulled it apart. It's kind of a pain to pull the instrument panel and I'm glad I had the old one to learn from. After you get it apart, there is a worm gear that is on some electric motor that just twists off. Before putting in the new one I suggest if you are changing panels to move the counter too. It pops out of the socket, but be careful not to damage anything! There are also two notches where it clicks in that help with alignment before fully installing it. When you are installing it, set it in gently and make sure you are on the correct row of digits then push it into the first notch. Finish aligning it and push it the rest of the way in. Now reinstall the worm gear and motor and reinstall everything. Now is also the best time to replace any bulbs that are bad so check.