You just do a simple Google search to find the manual for your cooker (then read it) or maybe some other helpful website.
Alternatively you could just throw your hands in the air and post a question on a random forum and hope that someone will answer without making sarcastic observations on the degree to which you didn't do anything to help yourself, before pointing you at a YouTube video he found inside 30 seconds.
https://www.youtube.com/watch?v=EASjhtxKr0I
If the timer IS knackered (technical term) you'll need to search for spares for your specific model of cooker, so find that out first.
espares.co.uk or ransomes.co.uk are pretty useful
Before you start working, make sure you have a pen and paper to make notes (Which screw goes where, which wire goes where) WITHOUT relying on memory.
XXX, January 2016
