Answers

If you want an efficient fireplace, I recommend a full insert (sealed-combustion) that runs a new vent pipe, typically up your existing chimney. Hire a professional installer from a local fireplace company to do this. 

There are also options to retrofit a "gas log" in an existing fireplace, but there are several issues with this. Typically, if you have an open hearth without doors that seal tightly closed (with a gasket) then you are going to put more energy up the chimney than actually radiates out into the room.

There are a very wide veriety of gas fireplace inserts.  

1. Check with the city to see what you can install.  Some cities are now requiring sealed units

2. Do not try runing a gas line by yourself.  Hire a licensed plumber to do it.

3. http://www.csia.org/?gclid=CL_Qk-SZ0dACFZBefgodOrUNRA Contact a CSIA certified chimney sweep to help you install. 

Thanks

Philip Anderson

HDR Remodeling Berkeley Ca