We used to rebuild heads and lap in new valves etc ourselves but nowadays it's not labour cost friendly so we literally send the head off to our local engineering shop and it comes back ready done as for costs u can prob go online and price up a new head set and bolts which should come with every gasket u need and timing belt kit and water pump. Then obviously antifreeze etc etc. Labour wise I've no idea what your man charges but at work parts and labour you'd prob not get much change out of £800 but my boss charges £60 plus vat an hour