American craftsman windows. Spring carrier

Thanks for posting. I believe this is a 15-087 Pivot Shoe. See the image below to confirm the dimensions match up. If so, this shoe uses Series 180 Coil Balances. You have to choose a spring weight for the replacement coil spring; this indicates the weight the individual spring can support. There should be a stamp on the coil spring itself (the spring on the actual shoe isn't always reliable to go by with this particular assembly). If there is no stamp on the spring, or you're unsure, tell me the exact weight of the window sash the balances support, and I can work it out for you.

Detail of 15-087

Yes, it's very straightforward. The 15-087 splits in half, vertically, allowing you to put the spring inside. You then just snap it back together.