You do not need a manual or a video, on the front of the apron first undo the nylocl nut on the engagement leaver.and lift off the cam cover, then undo the two allen screws on the top of the apron at the front edge. this allows the front of the apron to come away. At this point you will see two headless screws that engage with the engagement cam lever cover. remove them.
The two halves of the leadscrew nuts will be able to be withdrawn ( Note here:-that the one with the small grubs crew goes to the bottom) it's adjustment iis from under neath and needs avery small allen key which you will put away somewhere and lose!
Now you have a chance to clean the whole leadscrew thread and then wash all the parts in solvent and dry off. Note:- the half nuts will likely have some very hard stuff stuck in the thread.
Re-assembly should be easy enough and for lubrication use Graphite grease.