Hi and welcome!

The Nexus 5 is arguably the easiest device to unlock and root. Follow this guide by Chromium. (It's a sticky in the General section)

It's pretty straight forward, and doing it this way will help you out in the long run if you ever need to use ADB or fastboot in the future.

As far as issues go, there isn't anything worry about during the unlocking and rooting process. Just make sure you flash kernels and roms specifically for the N5. Also, be aware that not all kernels are compatible with all roms. Most Developers do a good job of explaining compatibility in their thread.

Good luck and enjoy!