1) You can use AMD overdrive. Google it to learn more or just head on over to the AMD website. Of course the original Phenom isn't too good of an overclocker.
2) The Phenom II is much better. The question of if it's worth the cost or not just depends on you. I say yes if you are going to overclock it, but if not then not so much. Head on over to the CPU charts to get an idea of the performance difference at stock speeds. Of course keep in mind that you can overclock a Phenom II to get some more value over it.