For a softer ride you can install Rodeo (or Amigo/Rodeo Sport) springs in the back, some comfy shocks (OME, Bilstein, etc) and 16" rims/tires. Springs should be easy to come by. I have a set that I'd be happy to get out of the basement, but anyone who's lifted a Rodeo has a set too. VX shocks are fairly stiff.
There are lots of options for shocks that will soften the ride. I'm partial to OME shocks but there are lots of other good choices. Going into things blind I might be tempted to get the Rancho 9000s just because you can adjust the firmness.
The comment on wheels/tires is related to the amount of sidewall. 18" tires have less sidewall than a comparable 16" tire. This means that there is less rubber to flex going over bumps. That's good for racing but bad for your kidneys. Maybe you can find a local 1999 VX driver who wants to just swap with you. You'll also find that 16" tires are cheaper too.
-Tad