If your thinking of propane let me know, there are things about installing LP that do not apply to natural gas.
About LP being dirty, what happens it Ethyl (ethyl mercaptan
) settles out/condenses in the bottom of the tank. Normally it isn't a problem as Ethyl is covered by the LP. When the tank goes 'empty' Ethyl is uncovered and starts remixing with he gaseous propane. This is the most notable time when propane burns dirty, and when dealerships start getting calls for non existent gas leaks. Seems Ethyl does not burn completely, especially ing the pilot lights, and the stink .... well, the stink makes it through the flame.
There are other reasons propane could burn dirty. Such as there being a NG jet, or out of adjustment, or the dealer could have contaminated the fuel in various ways (they may have filled the tank with motor fuel propane. Anyone growing a third eye?).
Far as plumbing NG, not hard at all. Hardest part about it has been mentioned, getting to the place to run the pipe, tearing out then fixing walls. No big thing for me as I'm an all around type of guy and serious DIYer, I already have the tools and experience.
Running the pipe itself is easy, or at least not that difficult. And doing it yourself isn't that expensive, and a bunch cheaper than hiring a plumber even after buying the pipe wrenches and other tools. Assuming there is already gas in the house.
What you need to do is read up on the Fuel Gas Code(s) to learn how to do the work. Location of drip legs, valves, pipe support, etc.
Then there are permit issues and such ... sort of .... and that's another story.