Blog design for dummies?

Well I'm clearly no pro at blog design, but I decided to mess around this afternoon and make a new header to go with my changed background. I've always taken backgrounds from Cutest Blog on the Block, but this time I made the header in powerpoint. I'm sure some of you may know an easier way I could do it, and maybe how to get the header centered on the middle column? If not, oh well, it's good enough for the next couple months until I'll begin to feel bored with it and change again!