I was able to stop at step 8 for the battery replacement.
Once you remove the metal shield, desolder the 3 leads. Then use your heat gun to warm the battery. Use plastic pry tool between copper backing and battery and separate them (two adhesive strips on the sides of the battery). Once done with this, you can snake the battery ribbon cable from between the logic board and aluminum casing. Not as easily, but still very doable, snake the new battery ribbon back through the same slot; solder 3 points and reassemble. Much easier than removing the entire board. Good luck!
Oh also, not mentioned in this guide - there is a plastic/silicon substance covering the 3 leads. Prior to desoldering remove this as much as possible with metal or plastic spudger (if metal, be sure not to bridge the connections).