Well, I broke my rule about trying out something serious (i.e. something that can and will go wrong) on another partition before applying it to my working partition. I installed Ubuntu KDE4 on computer G and experienced a lot of confusion. Today I decided to install KDE4 on computer S. S is the family computer and I should not change it too often.
I was very happy to see that Mandriva's KDE4 installation did its best to simulate what my previous KDE3 desktop looked like. The task bar and virtual desktops are still there. The icons that I had on my KDE3 desktop did not disappear as with Ubuntu, but were collected in a floating window called the Desktop folder. I should add that Ubuntu was a clean install so I might not have had any desktop to save. So perhaps this behavior will be the same with Ubuntu if one upgrades from KDE3 to KDE4 without re-installing.
So, where is my beautiful iceberg wallpaper? I can't seem to find it. I found myself on the wiki which reminded me of the cashew nut icon in the top right corner of the screen that I had seen and used on Ubuntu but forgot about. Left clicking brings out a semi-transparant menu behind my windows (I had to shift them away to read it). Right clicking brings out a menu that I can see above my windows. Appearance takes me to the Plasma Desktop appearances application. Nice.
Now I want to allow only applications on current desktops to be visible on the taskbar (which is not called that anymore, but right clicking I get "task manager"). The virtual desktop is now called a Pager. This is what had me stumped on Ubuntu. Now based on the recomendations here, I have to close all the windows to be able to right click on the taskbar (or panel or ....there should be a translation table somewhere). I'll put in a new note if it works.