Very cool stuff! I can't imagine myself rebuilding it, because I tend to have bad luck with things like that, but it looks like a great product!
Winding a coil and installing it isn't that hard. You wind 6 or 7 turns around the wick with a needle lying horizontally along the wick to prevent the
coils from being too tight. Leave the leads long enough to stick out the bottom of the tube once you install it. There is a silicone stopper that you install with one wire outside that contacts the outer shell of the tube. The other wire goes through the center of the stopper and a hollow plug pushes into it to secure the center connection. Once you have those parts in place, you clip the excess wire or twist them back and forth to break them off.
There are good videos that demonstrate the process. The most critical part is to make sure the wires are tight coming from the coil so that they don't touch each other or the center doesn't loop over and touch the outer connection.
At $1.60 each, it's easier to
buy new heads. I buy 5 packs for about $7.50.