Coconut

Hey guys, I have some newbie questions. I just bought a 93 240sx with about 130,000 miles. I person that I bought the car from said that he replaced the timing chain back around 100k miles, and unfortanly seems like that I'm have a problem like other people here on the board. I'm getting a tapping sound inside the cylinder head cover, and it's pretty loud once the engine warms up. My questions are, how hard is it to remove it? Is there a gasket that need tobe replaced? And what should I have to watch out for once the cover is removed. Thank you for any information.