well, the p&p is a mild one, and it is only on the intake side (or is it exhaust? i think its intake) if you change the cams, you dont HAVE to change the springs/retianers if you are keeping your stock rev limit. it is however a good idea to change them out, when i put in my ctr cams i put in itr springs/retainers because my ecu has no rev limit, and i like seeing my tach go to 8700

also, why are you boring over? are the walls jacked? if not, you should just stay where you are and not do an overbore. if you are doing it to acheive more displacment, it is not worth it for just that, only do it if you need to.