Oy. Never done one. Is that really the best option?
You can easily create a USB installer using Disk Maker X: http://diskmakerx.com (You may need to redownload the Yosemite installer from the Mac App Store.)
Then you just shut down your computer and restart holding down the Option key, and it will boot from the installer on the USB stick. You reformat and wipe your hard drive using Disk Utility and then install OS X on the wiped drive.
It's certainly a more intensive step, but it will essentially solve any problem that isn't hardware-based.
I don't understand why it needs to be so complicated just to upgrade an OS, ugh.
Sometimes things go wrong during installs, and over the course of time your computer is invariably going to get bloated with cruft of the system's making and your own. I clean install usually every other OS and it makes sure my computer is running the best it can. A lot of times the new OS isn't actually much slower than the old one if you take the time to clean up beforehand.