According to Buzzerblog, here are the details of GSN's tribute to Merv Griffin:
On Saturday from 10 AM to 3 PM, the network will show five hours worth of episodes of "Wheel of Fortune", one of which will be from the Chuck Woolery era! I like that.
On Sunday in the same slot, the network will show five hours of "Jeopardy!", probably from the 2001-2002 season they're running to the ground.
In the 3 AM-4 AM slot on the 19th, an episode of "To Tell the Truth" hosted by Merv Griffin will air, and an episode of "Play Your Hunch" will air.