That will be totally dependent on a number of factors that we can't estimate as they're to do with the garage you use and where you live. It also includes hours of labour, cost of labour, cost of parts etc. Your best bet is to call around to local garages and get some quotes. A stab in the dark? £400. The part itself is relatively easy to get, but it's a 3-hour job (roughly) and then then the oil will need refilling - which is expensive. I'd definitely get them to check it’s the oil pump, though. And pinpoint why it failed exactly. Otherwise, it’ll happen again.