Do it yourself

I'm hoping someone can direct me, my toilet fill valve will not shut off. No it is not the flapper, the tank fills up and just keeps on filling. The water level is over the float and goes down the overflow tube while the little hose that fills the bowl keeps going also. My brother put a new fill valve in 3 days ago--a fluid master--and it was working fine until the water was shut off to the house for a short while today. I have tried turning the water on and off to dislodge any debris in the seal but it is not working, my additional problem is the handle for the shut off below the toilet broke off. My plan is to put in a new shut off valve (hopefully not too difficult) and replace the water line from the shut off to the tank. Then see if that helps before replacing the fill valve again. I'm looking for pointers, advice, instructions on how to do this :D pretty much anything I can get. My brother is back in Florida so he can't really help. thanks suzie