re: rivets, pop them or drill them but they should go bye bye, its a reasonable step that only takes 5 minutes with a drill and a bit.
i'm assuming you have the hard plastic mats and they are getting "bumpy" for lack of a better description.
i've never been told that the adjesive seals the rivet holes, but imho it takes an extra $10 and 15 minutes to seal them with epoxy, so why skip the step, get it done right now and you'll be happy for a long time.
the actual hard part is usually getting the footwell clean of all dirt/grime/crap before installing the mat's themselves, this is the best time to get that part really clean since the mats will be out of the way for the first time in a decade
the last time I did this on a riveted mat, there were tons of junk/stains in the footwell due to the fact that PO's had stored the ski outside, the footwells filled up and sat so there were significant black stains... scrub that out (softscrub works well with a scotchbrite pad) 1500 grit wet sanding works well on the hard to remove stuff, just get it clean underneath where the new mats go and get it really clean around the edges of that area,
then re-apply the new mats.
all in all if there isn't a bunch of adhesive/glue stuck there (brake clean and a scotchbrite if there is) then the whole process will take about an hour's labor total, and you can take a beer break in the middle.
in the end, for about $100 the whole look of the ski will change, and will hold up for yrs with no leaks...
my advice is to not skip a step to save $10 (exoxy to cover rivet holes)