There is no easy way especially to do the least damage and, yes, they are spot welded on.
I have taken a spot weld cutter and removed them from the back side. If you are not concerned with salvaging the gutter, they could be taken off from the outside but likely the gutter would be ruined
Coupes are bad to get rust in behind the gutter and begin to waffle out with rust build up behind. When reinstalling, you have to be sure and seal well as that area could leak easily.
Some sort of body sealer on the welds on the inside.
That's a bad chore