I guess it depends on the filesystem of your root partition. Swap doesn't include anything "important" so you could just as well delete and recreate it, run the swap tools etc., but to increase it's size means you need to shrink the root partition. I'm not a master here, I prefer to think and create a working partitioning before rushing in..and you have backups, don't you, so you can try.
Half a gig should be enough swap. I have 512MB swap too, from an older installation, and it's definitely too much for my use even though I do run some "heavy" programs occationally. I've never seen it full, and most of the time I see it empty -- just a lot of wasted space most of the time. Especially after installing this most recent Slackware system my memory usage dropped a lot so there's even less need for swap.