Very dim screen after damage?

So about six months ago I accidentally dropped a glass of water on my Macbook and I took it to my local apple store and they told me it had water damage and needed massive repairs and I should just buy a new one because it would be cheaper, I didnt have the money for that so I took my broken laptop home and left it in my wardrobe for six months and the other day I was cleaning out my wardrobe and found the charger for the laptop and wanted to sell it but didnt know if it was workable as it got slightly wet in the water incident, I thought maybe I could plug it into the broken Macbook even though it doesnt work maybe somehow it would work and upon plugging it in the charger lit up! and then I left it for a good few hours to charge and when the charger went green I tried turning the laptop on and it worked but the screen is extremely dim, I was wondering is this an easy fix? or am I going to be told once again that the water has damaged it too much for it to be under $300? thank you for your time :)