Your springs and torsion bars don't really bounce as much as the old boats did, so it's a little harder to tell when your shocks are gone.
If they are leaking it's time to replace them
Here's a topic oddly enough titled How to improve your ride quality, which might help
http://www.automotiveforums.com/vbul...d.php?t=531075
Other than that you'll have to look into tuning it with different shocks, or even changing the tire pressure a little might help
Before you change shocks make sure that they are good quality