Fitting front Passat brake pads

Hello Everybody.
The brake warning light has just come on my 99 Passat so I am assuming the pads need replacing. I've got a couple of questions for you...How will I know if it's the front or rear pads that need replacing, Has anyone got a rough idea what this should cost, and is it difficult to do myself and will i need any special tools.
Many Thanks
Danny

Only front brakes has wear sensors fitted so you check them first. The rear pads dont wear to the same rate like the front ones due to the fact they dont work as hard. Its wise to remove the rear wheels and check them too as they will ruin the discs if they worn down to metal. Hope this helps.