The hole pattern is the same but they may or may not be able to reuse the holes previously drilled in the ski. Typically shops would rather redrill holes for a whole host of reasons mostly dealing with liability and the integrity of the holes already drilled.
As far as bindings work you would be much better of with an FKS155 or FKS 140 than stepping up to an 18 din especially if you plan on only setting the din to a lower setting. The springs in bindings work at a more optimal level in the middle of their din range than to either extreme. I am not saying it is totally out of the question for you to rock an 18 din but I think it is a much better decision to search out a newer fps/pivot 14 that has a din range of 5-14 which appears to be more appropriate for your height/weight
Ski Hard Because You Only Live Once.