Its only involved if you do it properly and turret the rear and re-enforce the beam, as obvioulsy the original shock mounts werent designed to carry the load of the car either through the shell or at that point on the beam.
But no one normally bothers with doing that when doing a road going clio (different if its going to be jumping hump back bridges on a road rally of course!), so its a very straight forward bolt on and off affair, shouldnt take anyone competant more than a couple of hours from start to finish.