This. A friend went down this route…. Purchases all of the hardware, but it had to go back to STEC to be checked / programmed. The fee for this and the STC at the time was 50% of the new cost.Before you go too far down the rabbit hole, check with S-Tec. My understanding is that they require you send the unit back to them for complete refurbishing, before they will issue an STC for your specific airframe. Then, you have to have it installed by an authorized S-Tec installer. It is often less expensive to buy a new autopilot such as the AeroCruze 100 or Trio.