i have been thinking of getting aluminum pulleys. They are awful expensive so i thought about just getting the crank pulley. is it worth changingall of them or just the crank pulley. will it give me a lot of power or just minor crap.

Minor crap. Not worth the time and money in my opinion.

Oh and for future reference, try to consolidate your questions into one topic... it helps keep the board clean and takes up less bandwidth.