water damage to logic board and power supply

I spilled water on the keyboard, a lot of water, while the power was on. I panicked and tried to soak it up with a towel but I heard some crackling and the power went off. I got the keyboard dry with the towel, there was some cursing going on, I started to calm down and I just sat there looking at a dark screen. The next day I took it to an Apple store and consulted the genius at the genius bar. He said the power supply and “probably" the logic board were fried, and who knows what else, and they could fix it for $1,000. Then he opened it up while he suggested that perhaps I should just get a new Mac. I think there was a MacBook Air selling for around a thousand bucks back then, it was 2013, but I didn’t want to get an air. I thought the best thing to do would be to think about it and not impulsively react. The guy suggested that it would be a good idea to remove the hard drive to keep it safe which he did. I wanted to accumulate some cash for a while and buy another MacBook Pro. A few months later I got a 13 inch retina with an SSD and I just forgot about my 15.

I’ve since retired and lately I started thinking about fixing the 15 myself. I think it would be a fun project. I saw a story on Google today about Apple not doing the battery replacements for old iPhones it promised for $29 unless “other damage” is fixed first. Then the story went on to say that iFixit was offering the repair for $29 and no hassles about fixing anything else that might be wrong. I checked out your website because I have an iPhone 6 that needs a new battery. I read the instruction for the battery replacement and thought I can do this and maybe I could do the MacBook too.

I need to know how to test components for damage and figure out what to do to get the 15 back up and running. I know the power supply and logic board should be replaced. I’d like to put a solid state drive in if that’s even possible and increase the RAM to at least 8 GB. What else can be or should be done? The 15 has been sitting there for almost 4 years now. Any help would be greatly appreciated.