Its really very simple. First, don't worry about them tampering with each other. Most Linux distos will show you Windows drives but it is up to you if you want to tamper with them, not the os. Windows will only show you the Linux drive in disk management.
In order to install on two different drives the easy way, it is best to install Windows first. So install your Win 7 on one hard drive, then install Linux on the other drive. Linux will install the Grub boot loader and you can select the os you want at boot. If you are new to Linux, Ubuntu is very user friendly. When installing just select "install alongside Windows" and it will install on the free unused space (which in your case will be the second drive). http://www.ubuntu.com/
If you are set on only running one drive at a time, you can use something like this, but in my opinion it is not necessary:
http://www.amazon.com/Drive-Switch-Controller--Orico-HD-PW6101/dp/B005NVV2GC/ref=sr_1_1?ie=UTF8&qid=1389758088&sr=8-1&keywords=hard+drive++switcher