I suppose you could try and unlock the bootloader without rooting. However, if you install a custom recovery without root, you may not be able to rename the stock recovery in order to have the custom recovery load.
I followed all instructions on this forum in order to minimize the possibility of a bricked phone.
I rooted first (http://forum.xda-developers.com/show....php?t=1940594
), unlocked the bootloader, and loaded a custom recovery.