firstly i assume i can rockbox the latest in the classic range http://store.apple.com/uk/browse/home/shop_ipod/family/ipod_classic yes?
secondly, does anyone know if there will be any issues using a rockboxd classic with a zeppelin air or similar dock? the only thing i'm thinking is i will have to boot into the ios part of the classic each time. is that correct?. http://www.bowers-wilkins.co.uk/Wireless-Music-Systems/Wireless-Music-Systems/Zeppelin-Air/explore.html
Yes, you can Rockbox it. Read the first post in this thread for all the steps and caveats, the chief of which is that using emCORE as the first step completely wipes iOS (i.e., the Apple firmware). Thus, there is no dual-booting (that could change in the future). It is possible to restore the Apple firmware (read the first post), but then, of course, you lose Rockbox.
I don't own any docks, but from reading this thread my impression is that iPod docks will not work once Rockbox is installed. You can get audio out of the USB port, but I think docks require the Apple firmware on the iPod in order to be fully functional.
Corrections are always welcome :-)