Well, that short css mockup can be really useful as of now. I already "stolen" some ideas that made my CSS work in IE7 too, and be more standard compliant and all (no more absolute positionings). I plan in stealing you the PNGs and the ideas to implement the tabs, if you do not mind.
For what concerns Plone/Zope, I advise you to read the Plone Book, freely available in PDF at
http://plone.org/documentation/manual/definitive-guide
(although you can buy it on Amazon or any other book store... I recommend it because printed books are much more handy). Pay special attention to chapter 5,6 and 7 (if I recall correctly).
Also, you should install plone on your pc/server/whatever in order to be able to test it on the fly before committing to cvs, else you might commit "blind".
That's almost all, and thnaks for the great mockup! ;)