With the shelf secure, get a couple of friends to come help, and stand the bench on its feet. I said earlier moving the top by yourself is dangerous. Trying to lift the entire bench is foolhardy. Of course, I already said I'm stubborn, so I did it myself by rigging a simple block-and-tackle using lightweight pulleys I got at the hardware store. (Not the lightest-weight pulleys, those are meant for flag poles and have a design load of something like 40 pounds. These had a design load of 420 pounds.)
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.