1990 100 cranks over, wont start

[TCpride]

on the first try, the engine cranks over and everything lights up, but it wont fire and then start. after the second or third try and giving it alot of gas it fires after releasing the key. it then has trouble staying on without constant acceleration (idles terribly and un-evenly, sometimes just shuts off again). a chevy mechanic told me it was a fuel system problem but i doubt he knows what he's talking about. is he right? my guess is it could be just bad spark plugs. anyone else have a problem similar to this? i'm going to change them tomorrow and will update with any progress afterwards.