Replying to Mounting question

I'm planning on buying  a used set of ski's- they'll be my first set.
They come with bindings, however they are unmounted and do not include hardware.

Iv'e searched, but I can't find anything about this.  Where do I get mounting hardware and how much will it cost me for it and the mounting?  If the holes are already drilled, will I be able to mount them myself or do I need a ski shop to do it for me?

They were mounted for a 27.5 size boot, while I wear a 28.5.  Can I use the same holes?

Thanks!