Obviously you want to remount a ski as little as possible, but these things happen and it's not the end of the world. However, there are a few things you want to make sure of when remounting. Before you mount the binders in their new position, line them up where you want them and see where the new holes will be in relation to the old ones. You should do your best to avoid drilling the new holes any closer than 1/2 inch away from the old ones. Doing so will potentially result in decreased screw hold in the ski and increase your chances of a toe/heel piece ripping out. Also, make sure you do a good job of sealing the old holes. Most shops should have little plastic inserts that fit into the old screw holes to help reseal the ski and make sure that no water gets to your core. All holes should get a generous dab of epoxy/glue followed by an insert and then have the excess glue wiped off and the excess insert, if there is any, sanded/ground off to make it flush with the topsheet.