Yep, also remember in the case of Guitar, Practice makes permanent, not perfect. So make sure what you practice is correct, can take a while to untrain yourself.
This is where I disagree, a guitarist not only has to come up with his part, he has to create the whole concept of the song, usually the song is about done when the drum part is added, even then there will only be a few drum styles to fit that song.
Any conroe cpu offers good performace, places like scan and overclockers are the best. As for Mobo, its very important to research it, as only the new ones offer conroe support out of the box, such as the P965 chipset.
I'd go conroe definantly for the cpu, as they are rather cheap in comparison to the performance they offer. 7600gt would be decent enough for the gpu. 1gig of corsair/crucial/etc would suffice. Tagan are good for psu's at decent prices.