I uninstalled my network manager trying to fix a problem. Now I have no network manager and therefore no internet. So I need one and I need to install it?
To install NetworkManager that is installed by default when you installed Ubuntu, just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command(s) below:
Thanks to vasa1, I failed to see the no internet part. So what you can do is visit Ubuntu Packages, from a machine that has Internet connectivity (friend's, work, etc.) go down to the bottom of the page, and download Network Manager that corresponds to your Ubuntu version and architecture (32, or 64 bit), (in my case its for 13.04 Raring) and once downloaded, take it over to your system, and install it from the downloaded file.
I did not realize the OP could not connect to the internet. You don't need a network manager to connect to the internet. Don't waste your time looking for a different computer and transferring the files. If you have an Ethernet cable connect the computer directly to the modem and then:
Append the following lines to the end of the file:
You should get an internet connection. If you do not have a DHCP server use the following instead (if you don't know if you have a DHCP server, then you probably have one so nevermind the following):
Replacing the address, netmask and gateway values with the ones you are used to.
If you cannot possibly connect the computer directly to the modem, you can also manually connect to a wireless AP, though it's much more complicated.
After connecting to the internet:
If you are not on the sudoers list issue