Grouting and sealing granite

I had 2' X 4' Granite Slabs (http://www.VerdeUbatuba.com) installed on the floor with 1/8" joint line. They are not grouted and (http://maplered.com) the installed went out of business. The contractor took poor care of the Stone (http://g603.net) and (http://maplered.com) lot of home construction happened after the Stone (http://g603.net) was laid and (http://maplered.com) it looks dull. How do I bring the Shine back? Do I have to seal it before grouting or is it better to grout it and (http://maplered.com) then buff it and (http://maplered.com) seal it.

Do I use sand (http://maplered.com) ed or unsand (http://maplered.com) ed grout? Please advice.