>I am trying to make a website that could use static GTFS data or data from an API linked to OpenTripPlanner for upcoming change of transit services in my area
For questions related specifically to OpenTripPlanner you're probably best off asking them on the OTP dev Google Group:
>I have some questions: is there a standard API format I have to follow if I create one?
If you're asking if there is a standard API format for transit data generally, there isn't for the GTFS ecosystem. The closest is the SIRI format - see MTA NYC's docs here on their SIRI-based API:
If you're asking about the OTP API, again, the OTP group would be a better place to ask questions. Here's the main documentation for OTP APIs to get you started:
>any tutorials or documentation that would be helpful on making this project?
Center for Urban Transportation Research
University of South Florida