My digital LCD instrument panel on my grizzly was not working. I took it off and unplugged it and found that there is a big crack in the top. When I put a new instrument panel back on, do I need to do anything special or will my current mileage and hours show up on the new instrument panel?

 

No, it will show zero miles and zero hours. You might check with your dealer to see if they can set it for you, but I doubt they can.
What they CAN do is authenticate the original mileage and the date the panel was replaced. That documentation will come in handy when you sell/trade the quad.