Water Damage/screen not working?/does boots up

My Nephew spilled water on his MacBook Pro and appeared to not turn on. He took it to Apple and they said it would cost almost as much as a new one. They did say they gave it a cleaning and dried it out, but still didn't work.

Apple said it needed a new logic board.

My brother didn't want to deal with it and bought him a new MacBook Pro.

My brother and nephew know I fix friends iPhones and Mac computers from time to time and they gave me the MacBook Pro. I turned it on and it does boot up but the screen does not appear to work, however if you look at it close in different angles you can see that it's working. It's like it just needs the brightness turned up but the buttons do nothing. I can't see the pointer, I move my finger around the touch pad but can't click on anything. So my question is, what do you think I should replace first, the screen, hoping that's what's causing the black screen. I have no money into this computer and it's not even 2yrs old. I have a nice 13in Retina and wouldn't mind having a 15in. around. Mostly I just want to fix it for the fun and experience. I don't mind putting money into it as long as I don't spend more then 80% of a new one. No really the the experience would be worth it!

Your help would be greatly appreciated!

Thank you, Kurt

I have plenty of ifixit tools to do the job and will purchase more tools if needed.

I own a collision shop so I also have quite the set of tools and a lot of electrical stuff that might help as well. But I do like ifixit tools made specific for this kind of work.

Ifixit makes not only all the tools needed in kits, they are also very good quality. I love my 54 piece kit and the new frictionless ratchet. Some very cool stuff!

Sorry for the long rambling email, just had a lot to say today I guess......