Don't forget to grease the threads of the new pedals to prevent them seizing and to torque them firmly with a proper pedal wrench to avoid them loosening and stripping the threads. I always use stainless steel pedal washers as an additional precaution against seizing and galling the cranks.
Remember that the left pedal has a left-hand thread.
Also, if the new pedals are serviceable I would suggest that you check them for sufficient grease and adjust them properly. It has been my experience that new pedals, even high-quality ones, come skimpily lubricated and adjusted too tight.