Upgrade to 5.1.1 Help Please

I've read around and see multiple starting points to do the upgrade and I guess I'm a bit confused. Hopefully you all can help.

I'm currently still on OB7 Stock 5.0.1 and rooted. I do have TWRP installed as well.

I'd like to update to the latest 5.1.1 and didn't unroot to get the little update between these two.

What's the best way to:

Update to the latest
Not wipe either of my storage areas
Not lose any settings
Gain root again

In other words, I'd just like to update and not flash a clean ROM.

I figure I'll probably have to use ODIN but I'm not sure which files to use or where to find them.

Again, I have read all the threads and they all seem to be different with different starting points and different issues.

Thanks in advance.