I'm a sub-contractor and the project we are working on is just about done. The general contractor is changing. Do I need to serve a new preliminary notice or is my original prelim sufficent?
Yes. Preliminary notice should be served once per contract. So, while change orders do not require further preliminary notice, a new contractor generally would. There may be exceptions to this general rule. But always safer to serve another preliminary notice. There isn't really any significant downside to doing so.