I strongly suggest to get a repair manual, read it, understand every step of it before you even touch anything. Start only if you feel absolutely confident about this job, otherwise let a VW specialist do it for you. If you make a mistake you can easily cause a serious damage to the engine. Better to replace the water pump, timing belt tensioner, idle pulley and front seals also while you at it.
You can find great repair manuals with step-by-step instructions, diagrams, parts locations and other important information here: http://bit.ly/mitchell_repair_manuals_online