Toyota Repair: Engine sounds like diesel after head rebuilt, toyota corolla, toyota repair

Question
hi, recently I sent my car to workshop due to gasket blown. It all started with this and causes water boiling in my radiator. The engine ran 200,000 km already so I decided to take this chance to overhaul the engine head.

Listing it out from my receipt, they changed these:
1. top set (japan) (gasket and all necessary items for overhauling the head. Comes in a set)
2. gein valve (they showed me, looks like a nut. They told me that there are worn out)
3. skim head
4. water pump (they found water leaking from the pump when doing the pressure test and advised me to change it to a new one)
5. oil treatment
6. water pump housing o-ring
7. distributor o-ring
8. engine oil

When I got the car, the engine sounds exactly like a diesel engine. The tapping sound comes out from the engine head. They told me that is because the valves are too clean as this is the first head overhaul after a 200,000 km usage. They said before the valves are cleaned there were very thick dirt and oil deposits where now it's all clean, that's the reason of the sound. They claimed that the sound will goes away after a few days of usage. It's 2nd day since I got back my car, and the noise is still there. I can't stand it anymore so I google this problem around and found your previous answer to a question:
http://en.allexperts.com/q/Toyota-Repair-832/5s-fe-making-tapping.htm

I am not sure if my case is the same as this one but it's clearly a diesel sound engine.

My car is a Toyota corolla 1.6 SEG manual, engine 4AFE, year 1997. Car is japan imported. I'm from Singapore.

I wish to ask you a few questions:
1. Will the sound really goes away overtime?
2. if I don't fix it, what is the worst that can happen?
3. If the head needs to be opened up again, do i need to replace the gasket again or it can be reused?

REally appreciate your help. Really need it as I'm worried about it causing new major problems. I usually use my car to travel very far so it needs to be in original condition. The sounds makes me very worry.

thank you.

Sean

Answer
The noise is not normal and it won't go away, they are either lying to you or they are stupid. The intake camshaft has a spring loaded two piece gear, a main gear and a sub gear, the two gears have to be locked together with a small bolt before removing and then removed after reinstalling it, ask them to check the service repair manual, if the gear wasn't locked before removing and then re-installed it will make the exact noise that you are hearing.