Can you comment on seam sealer recommendations andhow you "fill-in" the holes created by the self tapping screws. Some close ups with voice-over would be great!
There are plenty of companies selling a seam sealer product. We don't really have any preference to brands. You probably can go to your local autobody supply shop and have a choice of several products. As for the holes created by the screws, all you want to do is fill them in like you would do a rosette weld. Low settings on your welder so you don't blow through and start from the outside and work in.