Well in realistic sense if you need to save money cause you don't have much to spare, i could see just fixing the problem in the engine. but if you have some money to spend and some time (lets say its not your everyday driver) then i would say rebuild the whole engine.
www.whifbitz.co.uk has engine parts. you can also do a search over the internet for different part dealers. other option is they have these engines for bid on ebay with low mileage on them.