i need a bit of help. my trucks been havin trouble startin lately and im tryin to figure out if its the battery or starter or possibly the alternator. the trucks only got 30k miles on it. when i go to start it, sometimes it fires right up, other times it wont even turn over, but if i keep tryin eventually starts. sometimes its completely dead. i thought it was dirty terminals so i cleaned em with sandpaper. do i just need a new battey or is it possibly the starter. any ideas would be great. thanks. sorry for the mechanical retardation...