For the wireless question, I have written a reply in this thread: http://www.linuxquestions.org/questi...=1#post2764656
It's not extremely specific, but might stear you in the right direction.
As for installing ndiswrapper: Be sure to enable all repositories in Synaptic, and search for it. Tick it off and apply changes. It might be that ndiswrapper needs other small programs or libraries to run, but with Synaptic, it finds these on its own. You just have to answer yes when asked to install these other programs or libraries.
I can't say what's wrong with Add/Remove programs for you, as I am not as tech-savvy of GNU/Linux as I would wish. However, I had the same problem in both 6.06 and 6.10 myself. After looking through the list of programs in Synaptics with all repositories enabled, I decided it was a little more hassle finding what I wanted, but it was a lot easier getting programs suiting me. I seem to remember that Add/Remove worked for a few programs, then I installed something (don't remember what right now), and after that, it wouldn't work anymore.
I started right where you're at now, and I haven't gotten a lot further, but this is my experience. I am hoping that I have helped you somehow, as little as it may be.