My home was built in 1958 and has all the original terrazzo. There wasnever any carpeting laid so I don't have adhesive or nail holes. I would like to grind it down as it's absorbed discoloraion over the years. Someone said Home Depot rents orbital grinders. Has anyone used it andwhat are the concerns or pitfalls in using such a machine? What must be doe, if anything, to preparethe floors? Thanks for any advice.