deffinatly take it to a specialist! i wouldn't even trust a ford rs dealer, if the one in leicester is anything to go by i wouldn't trust em with a bog standard KA!
some places don't even rip you off that much on parts, i just had a cambelt change done on mine at GGR and it worked out about 8 quid dearer for them to get the parts than if i supplied them and i was getting them at trade price!