It depends on how much change you need and weather you are shortening it or lengthening it. You can sqeeze out about a half inch by twisting the string but I dont like going more than abouta 1/4 either way. To get a new cam you would have to have a bowpress or take it to a pro shop. Its pretty simple but if your a begginer I would just take it to a pro shop and let them do it. It probably would cost about 75 bucks for the cam and work, thats just a guess though.