Yes, they do help. They were a new inovative thing back when these cars were built. Now every car has them...even the cheap base models.
Installation is easy. If you aren't worried about a completely stock look, you can buy a brand new kit from Hotchkis. You'll have to remove the U-bolts from the rear axle so you can slide the end link plates between the springs and the rear axle perches. I assume new(longer) u-bolts come with the kit but I'm not sure. Maybe you don't even need longer ones?
You will have to drill holes in the frame rails for the swaybar brackets. The stock brackets are tapered to match the contour of the frame. I assume the Hotchkis one are tapered too. This makes it very easy to locate. The brackets basically locate themselves. Hook up the end links, swing the bar up into place and mark where you have to drill.
The hardest part of the whole install will probably be removing the old U-bolts.