DIY CAN Controller - Basics

Hello everyone,

I'm completely new here because I'm just starting to delve deeper into the topic of CAN (Controller Area Network). I own a private Audi A3 8P from 07/2004. I have a specific idea related to it, but I haven't yet explored whether it's feasible.

I'm envisioning building a kind of CAN controller that can read signals (values) from the CAN bus and display them on the upper portion of the FIS (Front Information System) display instead of the radio information. Instead of displaying the radio station, you could show real-time engine data that is available on the CAN bus.

My initial questions about this are:
- Are there small, freely programmable CAN modules that could solve such a task in a vehicle?
- Where can one obtain information about the existing CAN messages on the vehicle's CAN bus? Where might one be able to find a CAN database (DB) file?
- How would one build and program such a CAN module (that's certainly my biggest problem)?

If anyone has any ideas on this, thank you in advance for any helpful information!

Greetings,
Microphone.