I have both things on my To-Do-list. Unfortunatly my schedule is really crammed, and I still spend my "leisure time" on a bluetooth project with the Galileo.
At least you should give the Yocto Project Reference Manual and the https://wiki.yoctoproject.org/wiki/How_do_I a try. Especially the first one is more a "Guide for blind people who already know how to read braille and use a blindman's stick"[1], but knowledge comes with time (and the mistakes you make).
I already successfully created some recipes to make some permanent changes to /etc/fstab and /etc/network/interfaces to integrate a data partition on the SD card and to connect to my local WLAN without re-configurate this stuff after creating a new image. I promise to write about it in the next days.
[1] I'm aware that some Intel employees are reading here, but this is the exact feeling I've often got when dealing with opensource software projects where Intel is leading or involved. This includes, but is not limited, to Yocto, OpenCV and the Bluetooth-Stack on Linux called Bluez.