Unless you have a reason to believe your existing scores dont represent your ability I wouldnt retest. It takes time, money, and isnt likely to improve your chances.
As far as what scores to transmit with your app, I think it will usually help you to send as much info as you have. Some schools may pick the best performance from each section. Some may not. As long as you dont have anything truely humbling in the mix just transmit them all.