Is there a specialized wrench that I should use on this cap to the natural gas line? I'd like to install a quick connect valve for a barbecue hose
More importantly, at the local big box store, the attendant (even though selling the parts) frowned when I suggested I'd be doing the install myself. Is this task really so tricky and/or so risky that an amateur should not attempt it?
While the risks related to a leak are relatively low for someone properly trained , the fact that you might get your gas shut off by the town if the fittings havent' been tested and approved by their inspector means it's not worth that risk.
Gasfitting is not rocket science given the right training and tools, but the consequences of getting it wrong are severe, to you and your house and potentially to your neighborhood. I really, really recommend letting a pro handle it; they have the proper pressure and leak testers, they have the experience, and they have the insurance.
Is the quick disconnect rated for natural gas? If so a standard pipe wrench is used with thread sealant rated for natural gas. The yellow PFTE tape rated for natural gas is one example. This is a very low pressure fitting. When building homes with natural gas the line is pressurized to 30 lbs and a gauge attached the inspector checks the gauge and all the appliances then rechecks the gauge if there is any pressure change you don't get your green tag to allow the Gas company to hook up the regulator (also all the venting and connections to appliances, shut off valves must pass inspection). I used to pressurize the systems at the end of the day and check them the next day when I got to the site. If the pressure held I would call for the inspection. Since this is outside a good bubble leak solution could be used but this is not as good as a pressure check.