Oil change

Hi, i am about to change oil on my 86 300 e benz once this week, for the first time by myself, so i would like to ask how many qts of oil go in the oil tank, so that i know when i am buying new oil. Car has 200k+ miles, still runs good. What brand of oil or what type of oil do you recommend for my car. I think i had Havoline 10w30 on my last oil change. I am not considering any syntetic oil because i dont want no oil leaks( heard about that problem many times) even though it may work very good.
I figured out that i need oil change, also a yelow light for oil came up while driving on the interstate last night. Last time it happened i changed oil and it was ok after that(until now). Why the light is coming on when there is still enought oil( halfway between l and f mark). Truth is I didnt change oil since january mostly because i didnt even drive the car so much. have two cars
thanx, Alex