External regulator conversion question

I might be able to help with your pictures id you want to try transistor replacement. Transistors have 3 to 4 leads, go in one way. Likely surface mount. Typically cut two small leads close to part, then unsolder tails. The tab on the body under part, sinks heat, older parts have middle lead that is same as tab, on PCB thru hole. Surface mount uses tab and two leads. Some boards are not boards, but flex circuits using kapton (amber looking tape) and copper traces, bonded to aluminum case. I am not familiar with what a 93 has. I make my own ECUs, and able to fix most stuff. I help, but do not fix for others.