Here is an article describing how to reduce noise and voltage overshoot in buck topology DC/DC converters. Slowing down the turn on time of the high side switch in conjunction with replacing a diode with a low side switch should increase efficiency and lower the power dissipation.
Adding snubers (RC circuit) in parallel to the low side switch should help decrease overshoot, and lower noise. As always, the best thing to lower the noise is to carefully layout the PCB. High currents and switching operation can add loads of noise if the leads carrying that current are long, so keep them as short as possible.