What should I do?

I just bought a 99 civic ex and was wondering what kind of oil to use in it? Do I need regular oil or synthetic? The only mod to the motor so far are AEM cold air intake. I plan on doing alot more thought. Also where on the air pipe would I install the AEM Bypass valve? Does it go where the pipes meet or right behind the throttle body before the pipe? Thanks for the help in advance.