Be careful. Single 24x60" sheets of 3/4" MDF are pretty easy to lift. A doubled sheet is manageable. The countertop - 24x72" panel of 1-1/2" oak - weighs something over 100 pounds. It takes real care to lift safely. The joined top - 3" thick of oak and MDF - is past the range that can be lifted safely by one person. Don't try. Get a friend to help, or rig a block-and-tackle.
Grizzly is a company currently undergoing an upheaval. This brand was once known as a manufacturer of professional grade tools and equipment for woodworking products. Though, in recent years, that reputation has begun to slip a bit since being bought by the Chinese company SIEG. These days, whether the Grizzly product stands up to its previous standards of excellence often has more to do with what you are buying than the company itself.