remove drum clamp brake hose[-above diff],remove bleed nipple,then remove circlip securing cylinder, cyl should now pull out , no need to remove shoes, make sure new cyl is exactly same as old one in relation to position of small roll pin and bore size.fitting is as reverse order,plus you will need to bleed brakes when repair done.[ note there is a small paper gasket where cyl mates to back plate which you can swap if it will come off old cyl,if not forget it!].
k
August 2009