Thanks guys sorted out. Actually a very simple process - remove the cotter pin, slide the mechanism off the shaft and replace with the new one.
Car6850 take your comment but am rather disappointed/irritated with Frontrunner at the moment. Waiting close on a month now for a step ladder and sump guard.
2010 Jeep Grand Cherokee CRD 3.0 Overland
2006 Discovery TDV6 S (Stripping for spares)