Last neck I replaced was a few years ago. Not bad to do, it involves cutting off the old neck (or what is left of it) and making the surface flat (or smooth) and putting the replacement neck in place with an o-ring seal underneath, drilling 6 screw holes in the tank to attach it and you are done. With the gas cap in place, the mount is completely hidden, and the replacement neck is much stronger than the original one.
Not sure on the price but I think Image Enterprise is the only place that has them. The other option is to fin a replacement tank, but a cracked neck is real common problem.