Your confusion stems from the abstract nature of this conversation, I believe. If you purchased a bunch of wood, bicycle wire, canvas and a tractor engine and made an airplane, you would have infringed the Wright Brother's patent, even though all the components were free to use.
As for modifications (and repairs/restoration), that's a sticky subject without clear answers. Sometimes repairing or modifying a patented product for resale is legally akin to making an infringing product, other times it is not.
Adding more memory to product in the form of a bigger hard drive or solid state memory is likely not infringement, but you should clear it first with a qualified attorney who has all the facts.