Re: Ubuntu updates and bandwidth
First things first:
In Disk Utility, check the SMART statistics. Check how many "bad sectors" you have. Disk Utility has a warped idea of what is "a few" bad sectors; I recently encountered a disk with over 200 bad sectors. Once you have more than 50 bad sectors you probably need to back up all your data and put the hard disk into the rubbish bin.
If the SMART statistics shows a low number of bad sectors, like ten or twenty, you're probably okay to proceed. Back up your data to a different disk, not just a different partition, but you probably won't lose any data.
When you boot the Ubuntu 12.04 CD and start running the installer, it will ask how you want to install Ubuntu. One of the options will be "Install side-by-side with Ubuntu 11.10". DON'T choose that. Instead, choose the "Upgrade" option, and remove your 3G USB stick during installation. This will actually do a clean install of Ubuntu, but keep your existing files safe.
If there's no Upgrade option, you can choose "Something Else" and then simply find which partition you currently have Ubuntu 11.10 installed to, select it, click Edit Partition and set the mountpoint to "/". Click Ok and Next to start installing. DO NOT click anything else when you are on the Something Else screen.
I try to treat the cause, not the symptom. I avoid the terminal in instructions, unless it's easier or necessary. My instructions will work within the Ubuntu system, instead of breaking or subverting it. Those are the three guarantees to the helpee.