[Walperstyle]

how mild? if you are looking for anything over 250hp, you will want an o2 gauge and a good tune.

valve seals are not necessary if its not leaking oil into the piston chamber. But yeah, its only a few bucks to change them, so its up to you and if you have the ability to keep track of your buckets, shims and springs and such when you dismantle the head.