The masterbathroom in our new 10 year old home has marble surfaces on the floor and wall. Some areas in the shower stall are dull and have rust stain since we use well water, and the grouts are cracking. What kind of grout (grout for tiles?) should I use to repair the area? How hard is it to restore marble surfaces? Since I am not a very handy man, can I restore the surfaces or does the job require a professional?