most any computer can run ubuntu, if your computer cannot, try xubuntu or lubuntu. i got those running on a pentium 3. i doubt you are using something as bad as a p3.
do not have info you need on the usb drive as installing to it will likely require a format (well, not require, but it is the easiest way)
you should probably go with the latest version.
there are a million step by step tutorials, many in video form or with pictures. google is your friend.