Adding ESP32 to RC controller without frying either one

[-dr3x-]

I have a RC car controller that I'd like to add an ESP32 to so that I can control it via computer or phone.

Here are photos of the controller disassembled with the PCB displayed:
LANSU S&T LS-XLH223A-24GT

At the top of the PCB you can see two connectors, each with Red/Yellow/Black wires; one is connected to a trigger that controls speed; the other is connected to a knob that turns the wheels right or left.

I'd like to add in an ESP32, power it off of existing circuitry, and use it to intercept/log or inject signals at those two connectors. There are 3 AA batteries in the base of the unit. How do I do that without frying either the ESP32 or the controller?

Also I'd like to put a USB port on the housing so I can flash the ESP32 without disassembling the controller. The easy way would be to just run a cable out a hole but if not too expensive or difficult I'd like to add something more permanent.