Level of demo required for extending existing gas lines?
The problem with going through the ceiling, is going to be supporting the pipe. Even if you could feed the pipe through a small opening, you'd still have to open holes at regular intervals to attach the pipe to the joist. Snaking Corrugated Stainless Steel Tubing (CSST) through the ceiling likely would work, but again, you'd have to support it at regular intervals (3 - 4' I think).

I see three options.


Open up the ceiling along the entire length.
Go outside as Michael Karas suggests.
Run the pipe along the ceiling, and build a soffit around the pipe to hide it.