Thooks, the oil leak is pretty bad. if i keep the engine running for 20 minutes, all the oil will be lost! i can literally see an oil pond where i park my car.
since i found out about the leak, i have only driven it to the mechanic and back. and i had topped the oil then to make sure there's enough oil in it for me to get to the shop.

JimBlake, thanks for the info unfortunately, i don't have the time, the knowledge, or the tools to do all these works by myself - i can change the air filter and do these sort of small maintainance things, but anything more complex than that (timing belt job, flushing and refilling the coolant, etc.) needs to be taken to a mechanic.

as for the broken bolt in the air filter housing, i'll buy a new bolt+washer and will have the mechanic take the broken bolt out and install this new one...then i can change the air filter myself.

about changing the waterpump which results to flushing the coolant, do i need to use honda OEM coolant after that?