If performance is what you are after, you should look into an SSD for the system drive. As for installing Windows, yes, you can install from a USB flash drive. Many of us do that here, as it is quicker. There are some good guides in the Tutorials section. As for the actual install, if you can read, you can install Windows 7. It is, by far, the easiest Windows OS to install. You boot from the install media, follow the instructions, and then you are done.
One suggestion, especially for a new computer, don't put the license key in during the setup. You'll have 30 days to do this after the install. This gives you time to get the system up and running and make sure it is working right before activating. Even now, 18 months later, I still don't put the key in ever during the install process.