I was given a 7 year old bow, as a gift. I was wondering how much is too much to invest, in this. I invested so far 40 bucks for wb, 20 for sights, 10 for wrist strap. I want to get the cable/string replaced, they say its good. I don't know how it is under the serving, which looks good also. I am also new at this. I also invested 100 in tunning bow and arrows.