How can I make my old faux stone fireplace look newer?

Our condo was built in the 80's. It has a huge fireplace with "fake" stone on it. The fireplace actually has light brown grout between the stones that appears to match the same grout in the kitchen tile. How can I refresh the stones and grout to give them a clean, fresh appearance without actually having to remove and replace them? This same fireplace has three huge tiles that make up a raised sitting area in front of the fireplace, but years of candle wax, etc. has made them very unattractive. Any way to clean these up too?