The pucks have the frame brackets already there, you just have to buy the pucks. The only hard part would be drilling the holes in the correct spots, but they give you the measurements in the diagram/kit to layout in the bed. Also have seen where some have made cardboard templates to go on top of the pucks with the centers laid out.
So when you install the pucks, put the bed down back in place, drill a small pilot hole through the bed, the hole made by the drill is in the template. Slide the templates out and line up the hole in the bed and then make sure the center is where it needs to be and if it's just off, drill the new pilot hole through template into the bed and use the a correct size hole saw to make the holes in the bed for the pucks to work. Then seal the edges of the hole just made and then add the trim rings. Haven't done this yet, but have researched the best way to do this that minimizes any mistakes or off measurements.