Re: Converting propane grill to natural gas
They actually make a quick disconnect for just that purpose. I've seen them at the local Lowes and Home Depot. As for the conversion, kits are generally available from the appliance manufacture. I believe Propane and NG run at different pressures so you'll need to change the regulator as well as the afore mentioned orifices.
Changing the regulator.........usually not required as long as your downstream of the meter and regulator for the house.
Some conversions kits will come with a little replacement regulator with the proper orifice instead of having the consumer change just the orifice in some odd ball regulator.
I think as long as it is outside and not in a building, the connections do not have to be re-inspected each time you reconnect.
A simple gas **** with a downstream union may be acceptable in your area.
I would call your gas company or go online and see if they also sell gas appliances and grills to get all the right info and regs for your area. They should also be able to tell you what type og piping is required to get from your existing gas line to the grill.