It's not worth trying to repair a fan - you should replace it. Even WD40 will struggle to provide a lasting repair (though its often worth a go). Ideally you should buy exactly the same fan so that the fittings and the wiring are identical. Beware of the wiring - often fans operate from a light switch and have 2 live supplies one from the light another that is constantly live. So ensure that you can isolate the supply before removal. If you can't find the same fan - measure the diameter of the old one and get the same. (They're not very expensive - DIY and electrical suppliers keep loads of different makes and sizes in stock). Follow the manufacturers installation instructions - if you're in any doubt you'll have to contact a local electrician (that might be a bit more costly).
phil@recreations.co.uk, December 2006