[ubuntu-uk] Help gnome 3 broke my laptop!

[Pete]

hi all,

I was playing around trying to install gnome 3 onto my Ubuntu 11.04 
system, this was done via synaptic, since then I have been given the 
choice of 'gnome classic, KDE (plasma workspace), Arios (my original 
system based on Ubuntu), recovery console, unity 2d, user defined 
session' at login but none of them are my original desktop session and 
most give the error 'unable to load session' with the option to logout.

I have since got the KDE desktop working to write this post.

I have 'completely removed' gnome 3 in synaptic but it only removed 1 
package not the 139 it installed when I installed it!

My question(s) are

1/ most important how do I recover my original desktop session?
2/ why did it install the KDE desktop environment without me even trying?
3/ is there a way of listing the packages installed on a certain 
date/time to ensure I can manually remove them with the hope of 
restoring my system to it's previous state?

thanks in advance (and no I will not be trying to install extra desktops 
on an existing system again, I will dual boot in future!!)

regards

Pete