Anything that will cut wood will also cut plastic. A saw with finer teeth, like a backsaw, will leave a smoother cut. As far as resale value of the gun, I would order a replacement stock and cut that, then you can put the original back on when you want to sell. I have done this with wood stocked guns. I have also cut the original for a child and then bought a full size when he grew. The extra "youth stock" thrown in can help make a sale.