Hacking my pioneer 7200 head unit

I have a pioneer head unit in my truck, avh-7200 or something along those lines, my ultimate plan is to hack the can-bus of my truck and display data to an extra hdmi Input on the radio( probably with a raspberry pi or similiar I’m imagining), however a big part of that plan is that I want to use the existing touch screen of the radio as my interface. That’s where the arduino will come in handy I hope.
I’ve already taken a look inside the radios screen and followed the 4 wires from the resistive touch screen to an ic called AK4187, which is a touch screen controller,
The main way this ic communicates is via i2c, so I’m planning on intercepting it’s normal conversation with the radio, parse out the X/Y, and then send that to my main brain as a mouse input(current idea of simplicity, using a arduino micro)
Not too worried about the hacking of the i2c signal progmatically, the data sheet should be all I need for that, I’m just worried about ensuring my 100$ project doesn’t fry my 600$ radio

So now the real question is what’s the simplest, least risky way to snoop in on those i2c signals?

My ideal so far is to tap into 4x locations, the 3.3v+, gnd, SDA, and SDL
I’ll hook up high speed opamp to buffer the signals thru to a pair of opticocouplers, which then after that I’m Scott free to do as I please (level shifting as needed etc) without risking damage

Things I don’t know -
Is the above actually feasible ?
Is there a simpler easier way?
Can i2c work that way where it just listens and never takes control of the line?
Am I way too worried and should just hook my arduino ground to that ground and inputs right to my i2c lines of interest?

I think a few little resistors on your lines would be polite, just while the Arduino may be booting you don't want to upset the lines too much.

As far as I know you can just monitor the Clock and Data lines and decode as if you were a slave device.
There must be loads of that code around.

Oh I see the mention of a 3.3v voltage.
Make sure that things are all working at the same volts or use a level shifter on the lines to bridge any voltage gap.

Unless you know the ability of the 3v supply to the AK4187 I would not be connecting to it for any power needs, just a reference perhaps for the level shifter.

Opto-isolation is the more professional way but it depends on the needs.

As normal most of the hardware protection is there to protect it against the human.!!

As long as you limit the maximum voltage and limit the current drain, The worse that can happen is that your touch screen becomes unresponsive while connected to the secondary interface. If you start pulsing 12v down those wires, you wont walk away laughing.