Plumbing in a new gas line

The local fire marshall and building department have dictated that there can no longer be any propane fueled grills on a deck attached to a dwelling. I'm going to change the jets and any other required parts on my grill so I can plumb in natural gas to it. One neighbor had a plumber do his using flex pipe to the quick disconnect and shutoff. While that would be nice, it seems you can't buy this (flex and fittings) unless you are certified in its installation. The existing internal stuff is black iron. I've got a T with one outlet capped that can be used to supply the new line.

Are there any special points that I should be aware of if I do this myself (otherthan blowing myself up?!)?

The main shutoff valve is a one-way valve; you need a special tool to turn it back on. I've actually made one that works but was told that I could have problems turning it back on because a slug could fall and (intentionally) plug the line. Is this bogus? Is there a visual way to tell if this is true (if it is used some places)? Have I been lucky the last 2-3 times I shut it off to do something?

The last time I did this, I found out that the main shutoff did not really fully shut off the the gas (it did slow it down alot, though). When doing some changes with the main valve off, I found that I needed another fitting, closed up the door, ran to HD, and found a bunch of gas when I returned. So much for the gas company's shut off. with this in mind, should I consider having a pro do this operation?

I found a nice 360 degree swivel in the Grainger catalog with an integrated quick disconnect and shutoff. While this may be overkill, would you recommend this, or should I just use something rigid? Note that the grill will NOT be bolted down and can be moved around.

gas

As soon as you said you closed the door on a leaking gas system, and left it, I decided you need a professional plumber for the job. Otherwise you may be the featured story on the six o'clock news. There are gas meters that have to be reset when they are turned off, but if yours has not needed it previously, then you may not have that type. A professional plumber might use the flexible pipe you referred to.

While working on it with the main valve closed the first time, it was by the opened back door, and there was no gas smell - it is a very small leak through the shutoff. When you close a main valve, I made the (dumb) assumption that the gas was off - otherwise, why have a shutoff. There was no smell of gas leaking when I left, only when I got back. Since then, after realizing it did leak, I've been very careful and quick to cap things off when making any other changes with lots of ventilation.

I was just wondering if there were any special considerations I should be aware of in this situation. I think that I have enough room to thread on a shutoff valve right there where the tee is capped right now, and if I do open it, thats what I'll do. The t is pretty close to the wall, so I'm not sure anything other than a straight pipe or an elbow can be screwed on without taking some drywall off.

Answers to the other questions?

I'm tentatively planning on having the boiler replaced, and may have them do it at the same time, but I'd like to get this resolved first.

Quick Disconnect

A regular ball valve shut off should work. Mobile homes have a plastic nipple and a disconnect valve that shuts down the gas if the line breaks. I don't know if that would be appropriate for your use. A quick-disconnect appliance connector may also be considered. I have just been installating a regular flex connector.