I just upgraded to kde3 by putting these 2 lines in my sources.list.
deb http://kde3.geniussystems.net/debian ./
deb http://people.debian.org/~bab/kde3 ./
Then just ran apt-get update and apt-get install
I didnt remove any kde2.2.2 stuff, it was removed as the install of kde3 was taking place.
I installed kdelibs 1st then kdebase then arts, after that it does'nt matter in what order you install any other kde progs, seems to be working well.
BTW: It also uninstalled koffice, so i will have to re-install that, if there is a version available for kde3