Water spill, MacBook works but display is white

I'm a Mac enthusiast that's been helping friends and family become Mac users for years.

Recently one of my 'customers' spilled a glass of tap water over her MacBook Unibody which was switched on and running at the time. She said most of it went on the keyboard, but the screen may have been splashed too.

She didn't turn it off - it shut down by itself, apparently. She didn't do any of the things you're supposed to do (turning off the power, removing the battery, puttting it upside down to dry, etc.) and didn't tell me until a couple of days later. So it was basically too late by then.

I received the machine a week ago, promptly dismantled it to see if it was wet, but everything was now dry. I left it all this week to dry out, but no change.

The machine boots fine (correct startup chime), but the screen doesn't show anything. It's just white. The backlight works fine but the screen has developed some faint vertical stripes.

I connected the Mac to an external screen today and used Cmd-F1 to get it to display on the external screen. The Mac seems to be running fine apart from the screen issue.

I have now backed it up using Time Machine, but I just can't get the internal display working.

What's next? A whole new logic board, or is it the screen that's defective?

Does anyone have any experience of the companies and individuals offering cheap logic board swaps on eBay?