If ASUS backs the bigger CPU I'd go with it. You can't go wrong and it will safely will OC to 4gb's after warrenty runs out.
And by then you'll be an ole pro.
Don't worry about building your own rig. By your posts over time I've always been impressed with your common sense as well as humor.
Spend $2.00 on a ground strap. Buy it locally and they'll show as well as explain it's worth for a newbe builder.
As far as cases go there's so much variety, price and.......
I think your onto a fun adventure that should make you proud when your done.
DOWNSIDE : Your family and friends will bug you to help them upgrade.