Damaged motherboard, is it worth fixing it?

In 2010 I bought a new (at the time) Macbook Pro 13" for college. Well into it's second year, it was inside a bagpack with a water bottle with a cap that was a little loose, and water slowly leaked inside the bag. The computer was in a seperate sleeve and pocket, but said sleeve, got wet in a corner and humidity (or water) made it's way to the motherboard (this is what I was told).

I took it to get it checked, and the they told me what I've just said; the motherboard died, and at the time, they told me replacing it would cost around $800.

A family member gifted me another mac, and I just left the 2010 one there, didn't replaced the motherboard or sold it.

What I want to know is:

1) Is it worth fixing it up now?

2) How much would it cost to fix it now?

3) How much could it be sold for, now, as it is (without the motherboard)?

(the computer it's in pretty good shape, it has a small bump, but nothing drastic)