This thread is to mostly thank Hepar for the donated rack bars and to comment on the generousity of this forum. Most people have been willing to donate or sell for cheap the parts I need.
Super easy. If you have the flat slats on top you just unscrew the 10 bolts, remove the flat slats, assemble the new rack on the ground, place it on top, and screw it down. I put silicone in the holes before I put the bolt in to ensure it didn't leak. YMMV
You wouldn't necessarily have to assemble on the ground but don't screw the 2 front or 2 rear bolts down until you have put your crossbars in the tracks and get the endcaps in place. Those bolts would go in last.