I sharpened a mower cylinder on a friend's 14" Qualcast last year without dismantling it...
I took an oilstone to the rotating blades and honed a clean edge on them - then I cleaned up the fixed blade and then set the edge for a clearance/interference fit. A check by hand with a piece of paper showed it cut like a pair of scissors. Friend very pleased.
If you really wish to strip it down you can find lots of exploded parts diagrams here...
http://www.mtmc.co.uk/default.asp
Look under Spare Parts Qualcast Classic Petrol 43S (10 models)
Good luck...
Took a couple of hours. Much easier than dismantling
Peccavi
March 2010