I've done this work and it isn't hard. I have instructions on the Ford Focus Electric Owners' Group on Facebook. Go to that and and request to be a member. Once in, search P0AA1 and look for my writeup. Pictures and everything. Here is an idea of what I did.
-Buy 1K high voltage gloves
-Buy an insulated metric socket set
-remove the rear bench seat. I don't think I took the backs off, but it would have been a little easier.
-Take the two service disconnects off
-Remove the plastic cover behind the rear seat.
-Remove the trunk liner that covers the battery.
-Remove all the bolts around the battery. A few, in the corners, are a different length, so keep a note of what goes where.
-The metal cover is also glued, so you will need to use something thin to break the seal and pull the cover off. Not too hard.
-On the driver's side, you will see the orange cover over the contactors. The cover comes off easily, but you will need to do a bit of disassembly to get the bus bars off.
-The contactor control input will need to be disconnected and removed. I forget what it was about that connector, but at first I tried too hard, but it eventually came off easily. I had to cut the wires off of the contactor and solder to my new one. The bad contactor will be discolored on top.
-Solder the old wires onto the new contactor and put into place
-Put the bus bars and circuit board back into place.
-Using a torque wrench and following the specs for the contactor, bolt down the bus bars onto the contactor.
-Put the service disconnects back in.
-Test the car.
-Remove the disconnects again.
-Put the contactor cover back on.
-Put the battery cover back on.
-Put the trunk liner back in place.
-Put the plastic cover behind the seats back on
-Put the seats back in
-Put the disconnects back in.
Steps along the way...have a volt meter to double check anything you are about to touch...even with the gloves. Everything should be zero, but you want to make sure. Yeah, you can save a lot of money, but it isn't worth dying for. Anyway, look at the facebook page for my write up. I think I have a couple of posts about the process and I did it so it could be followed. I took about 2 weeks to do this. I did it slowly and carefully.
