Given your history with bb I'm pretty sure you can handle it.
The Dev unlock opens up the bootloader and allows the toolkit to install recovery. Take your pick, though I think twrp would be better for you.
First thing after rooted and recovery installed would be to do a nandroid and copy it to a computer.
Not sure how to boot to recovery on that phone but I know it can be gooooooogled. Usually holding a combination of power/volume during boot.
If you install twrp then you'll see a screen with 2 rows of buttons. Choose backup and just swipe the slider at the bottom. Will take a few minutes. Then hit the home button within twrp (home plate looking icon) and choose reboot, then system.
Get a file manager. ES is free and great. I prefer Root Explorer but its not free. Open ES, choose sd card (be sure to have connected to pc), scroll to twrp folder, backups, there will be a folder with a date format. It will be pretty big, copy to of for safe keeping.
Now once you root I strongly suggest buying titanium backup. Its the best backup for your apps and app data. Never restore system data using.
Take your time. If you hurry and skip reading you risk missing something and getting frustrated and annoyed.
Toolkits are OK, and good for this, but after you do it learn fastboot commands and adb commands. If you can get fastboot under your belt you'll be golden. I still have to look up commands, but unless you hose something you wont need them very often at all.