I've found a flasher module I like and id like to have it do all 3 brake lights. Would prefer to only buy one so where is the main wires for the brake lights that I could install it into. Or would it be better to find a shop to do it for me if it's too hard to get to those main wires. Would also...

I bought a 2008 wrx about 4 months ago without the sellers having any knowledge of what was done to the car, turns out that it was an absolute steal because of that one reason. But without the owners not knowing what was done to it, I know very little about what is done to it internally. I know...