Normally the gas fittings/plumbing in a campervan (for example) are made up of solid pipes secured to the inside of the vehicle distributing the gas to the applicances, but at each end there is a length of flexible hose which is what allows you to attach the cylinder or appliance with ease. In my (not huge) experience the hose is pretty standard stuff.
The regulators are definitely seperate and removable from the hose. I have done this a number of times. The best way is to soak the end of the hose in hot water for a few minutes (which will soften it easily) and then just push it onto the regulator.
Obviously with gas make sure that whatever you do on one end of the hose doesn't loosen the other end. This should be relatively easy because the other end of the hose should have a screw on attachment to fit to the distribution end.
To answer your questions (bearing in mind I haven't seen your specific fittings) :
1) yes, you can just snip, remove and then add the new one (using hot water as above to make it easier)
2) they are normally distinct units as above. A smell of gas is normally not good, but is to be expected when removing the regulator from the cylinder as the valve will be open for a tiny amount of time as you remove the regulator.
z