Google’s Nexus 7 is a good powerful device. It’s Nvidia Tegra 3 chipset having the Quad-core 1.2 GHz Cortex-A9 CPU is a powerhouse. Google’s Nexus series is known for it’s extreme ease to root as well as unlock bootloaders. The same applies for Nexus 7. This is a Guide to Unlock Bootloader as well as Root your device. To know more about rooting see this article.
Note: Unlocking the bootloader will cause complete data loss. Hence it is advisable to backup your messages and contacts.