Unless you've got a lot of experience with this, or have the tools needed to polish granite, then I think you're biting off more than you can chew. Making and installing a granite counter top is not a DIY project except for someone who polishes granite headstones, or has the tools and equipment to do that kind of work.
If you have a square edge laminate counter top, my advice to you would be to remove the laminate from the counter top, and install a prefab laminate counter top over your existing plywood. That IS a DIY project, but it's still gonna require you to buy about $300 worth of tools and $100 (or more) worth of prefab laminate counter top, and some plastic laminate to finish the square edges of the top you have now. That can cost anywhere from $4 to $60 for anything from a handipanel to a 4X8 sheet of laminate.
If you want to see what such an installation looks like, I've done it inALL but one of my 21 kitchens, and you can see pictures at:
You'll need a plastic laminate trimmer, an electric drill, a jig saw, a belt sander, a bastard flat file, a 3/ 16" chain saw file, and maybe a fine flat file. And, of course, you're going to need a helper occasionally to lift the top into place to mark it, and take it back down again to cut it. But, that's nothing compared to the cost of the grinder and diamond disks needed to polish granite.