new cam for 00' Z71

been reading on some past threads about swapping the cam out for a more aggressive cam like the ls1 cam. was just wondering if anyone has done this and how much it cost. will this hurt my gas mileage? and what kind of power gains could i expect. any other suggestions for performance upgrades are welcome. so far a flowmaster 40 series exhaust, and a aem brute force intake on the way

thanks for any help

sean