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Yep - the 2.0.16 upgrade from 2.0.15 is simple to do. Just upload the files and excute a script via your web-browser.
As for newbb, I'd give is a miss and get CBB 3.07 (and the xoopseditors and Frameworks) from the Dev Forge. Although called CBB, its really the latest version of newbb - even the module directory is called newbb
Not sure I understand what you mean about the theme. Some themes are two-column fixed-width which might be an issue for you.
I've gone with a theme called "bizlook" and you can download the latest version from the My Web Resource website.
The theme has a simple to vary "wrapper" which means that you can set the screen-width occupied simply by editing one number in the style.css file. I've set mine to be 100%, but it comes set at 95% anyway.
The standard "bizlook" colours are a but dull (to my taste anyway!), but it's really easy to alter the colour scheme as style.css is logically labelled. Mine doesn't really look anything like "bizlook" anymore, but the changes didn't take that long to do.
As already suggested, perhaps you could post the URL so we can take a look?
Don't give up