I'm no expert, but once you have the lines added to your source list, A simple apt-get update followed by apt-get install task-kde should take care of it. You might need to add other packages seperately. I'm not sure what is included in the task list. I was using 2.0.1 before I wiped my system. I'll be updating to 2.1 once I get my new system working 100%. From what I've seen on this list, though. 2.1, despite being 'beta' seems to be quite stable and useful. There seems to be a few small issues, but I don't think anything to be too worried about. And Ivan is extremely helpful as well! Youi also might want to look for the Debian-KDE FAQ. I'm not sure where it is on the web, but I can send you a copy if you ask. This should give you some more info.
I hope this helps. Like I said, I've found this list to be quite good and we are all indebted to Ivan for his hard work and dedication to making sure that Debian and KDE play nicely together Cheers, John Gay