How can I fix the cooling fan on my Kenwood CK780 cooker?

I have inherited (bought with house) a Kenwood electric range cooker (CK 780). I think the cooling fan is faulty as it makes an loud noise after the oven has been on for a little while and continues until the oven has cooled down. I have been unable to get local repair people to look at it as its an unknown brand to them! Curry's - where it was purchased won't help as I don't have a receipt/bought date. So looks like I am faced with fixing myself!! Can anyone help and advise how I go about this? I have an instruction booklet but no info on how to access the cooker to carry out repairs. Where do I begin??!