First, you need to determine exactly where the damage lays. Can be the screen, can be the logic board, can be just a cable. So the first order of business is getting it assessed. An Apple Store, an authorized service provider, etc. May charge you for the assessment, especially if you don't leave it for repairs.
As for parts costs, once you know what parts you need, might want to check at places like www.ifixit.com or www.powerbookmedic.com just have the model number handy.
Take the broken computer to an Apple Store for a free diagnostic test. Ask the repair tech how much it would cost to fix. No one here can tell you because we don't know what is wrong with the computer.
It is at least 6 years old
MacBook Pro: Distorted video or no video issues . The affected computers were manufactured between approximately May 2007 and September 2008.