When to DIY vs when to call a tech

A rough rule I use myself: if a mistake just costs you time or a part, DIY is usually fine to attempt with some research. If a mistake could mean structural damage, a safety system (brakes, propane, high-voltage electrical), or something that gets much more expensive if done wrong, that's when calling a tech first — even just for a phone consult — is worth it before diving in. What are you trying to decide on?