Floor pans. gulp...help...

That's one thing I have to pick up is a spot weld cutter. I'm not reusing the pans so I could prob just grind the welds down til I get the cutter. I have all the necessary tools I'm an auto tech so I have my arsenal of tools lol.. should I just spot weld the pans in or should I do solid welds I'm sure the spot weld would be much easier since this is my first floor pan job.another thing after I get all the panels welded in should I use seam sealer around the seams and I'm planning on using some pretty loud exhaust any opinions on the dynamat?