It's attached with rivets - you can buy a tool-less rivet kit like [http://www.pinbits.com/index.php?main_page=product_info&products_id=72] which works, but it was a bit hit-or-miss when I did it. I finally got a good, lasting pair of rivets in there, but I'd never done it before and it took several tries...

Just remove the bolts attaching the ramp assembly to the solenoid assembly that holds it and remove it from the top of the playfield. Drill or use a punch to hammer out the existing rivets and replace the ramp with the new one. Not too bad, though as I mentioned it took me a few tries to rivet it properly.