Do some research for your job first, the internet is your best friend! And I think I mentioned an off duty plumber is what you want to hire not some jerk that sells concession trailers and can't wait to rip you off.
After one search here are two good links for you to start :
We have all been taught that running a gas line is so dangerous, you should just not bother. Just pay the professionals. This sort of teaching breeds ignorance and in a time of crisis when there's no plumber around, you might be S.O.L. One thing that I like to remind people is that most people with a normal sense of smell will be able to smell a gas leak way way way before it is going to do any harm (assuming the gas is collecting in a relatively enclosed area).
http://xj.cdevco.net/gas_line/ 
by
Ryan Grimm » Sun Mar 27, 2005 8:56 am
There are two main systems for propane lines, copper and black iron pipe. There are stainless piping systems that are available, but these MUST be installed by a licensed plumber, and at any rate I do NOT know if they are listed for RV installations.
Both copper and black iron have their advantages and disadvantages.
Copper is amazingly flexible, relatively cheap, easy to cut and splice, add tees or cap off dead ends.
Black iron is heavier, rigid, requires more expensive tools to cut/thread/install, and is sometimes difficult to get cut to an exact length for a small space. Plus, I need unions to break long runs into managable lengths.
http://www.skoolie.net/forum/viewtopic.php?t=569 And there are a ton of links on this subject online all you need do is search. But don't just read one or two spend a couple of days searching and reading, and soon you'll have the knowledge and confidence to do it yourself or know if your getting a fair price from AN OFF DUTY PLUMBER. By the way the younger plumbers (in the trade for just 2 to 4 years) are best because they are still hungry, and looking to keep more money coming in. The older guys know they can get big bucks at work and are less inclined to do after hours jobs and they'll want big bucks.In fact I had a job I could not do this last winter and the going rate here is $85.00 per hour. That sucks so how much is your time worth to DO THE RESEARCH. LMAO
Good luck