Not as difficult as you might think. 20 - 30 mins
Nip down to the local DIY store and buy a new syphon to match, or similar to the one you have and also buy a donut washer & plate (kit about £5).
Turn off the water supply and flush the loo
Take lid off cistern
Reach behind WC pan and find two wing nuts one each side pointing down - slacken them off
Remove the two screws at the back of the cistern - inside at the top
Carefully lift the cistern upwards and tip any excess water back down the pan
Remove the big syphon nut underneath and lift out the existing syphon - pay attention to washers etc.
Fit new syphon, new donut washer and re-saaemble cistern to pan and wall - do not overtighten wall screws else you'll risk cracking the cistern
Do up donut wing nuts
Turn water on - check and adjust fill level if necessary
Put lid on
Check donut seal for water tightness
Work of this nature is not the exclusive province of men - the toilet is not bothered by your gender - ironing however is a different matter altogether.
Carry on as normal
Peccavi
December 2009