The latest version of wicd in the Ubuntu repositories for 12.04 is 126.96.36.199-1ubuntu0.1.
To upgrade a specific package(s) via apt-get, you simply use
sudo apt-get install wicd
If a newer version is available, it will be upgraded, otherwise apt-get will tell you:
wicd is already the newest version.
The Chrome thing looks like a PPA you added which is no longer available for your Ubuntu version.
upgrade tries to upgrade all packages from all repositories, hence the 404 error. It doesn't matter unless you want to install/upgrade Chrome, but you can remove that PPA from Software Sources to get rid of the message.