So a .iso is currently downloading onto my flash drive. After that, what do I do? I'm just scared of deleting Windows 7 and all my files.
You're doing it a bit wrong. You shouldn't copy the ISO file to the flash drive - you need to use some program to "burn" that iso file to a CD or to a flash drive. Burning a CD seems to be a bit easier than preparing a flash drive - for the latter you'll need to somehow "open" the ISO image and extract usb-creator.exe program from there, so you'll need some software to work with ISO images anyway.
Then you'll need to reboot your machine, enter BIOS setup and choose your flash drive/CD as the first boot device. Then you reboot with the usb drive/CD inserted and you get to the "live" ubuntu environment, from where you will be able to start the installation process. The installation process should be easy even for an inexperienced person - there are just 6 or so questions. And it won't erase your files unless you explicitly tell it to remove the Windows partition.
Having a backup of your important files is a good idea in any case, even if you weren't installing Ubuntu.
Another thing to mention - you could install VirtualBox and practice installing Ubuntu inside a virtual machine first.
Also, you could order a CD from ubuntu.com if you still having trouble with preparing a usb drive
Go to ubuntu dowload page and follow their, very clear, instructions (There is a big red button there, ``show me how''). If you want to do something a little bit more exotic tell us what you want to do.