Before you start pricing out parts you need to figure out the problem. Will the light show up that the heated seat is on? If so have you tested the wires for the heating element to see if it is working correct? I believe the element is fairly cheap for the seat, maybe like 20 bucks. I do not know how much the switch/button is. You need to explain further on the rev shaking. The LS only allows a certain amount of rpms before it kicks in the rev limiter. Yes it is very low, Like 3000 rpm or less. If that is the problem, get a tune done on it to kick out the rev limiter. It is fairly costly (400 or so).