Dumbest thing I have done in a long time was to make a quick purchase decision on my Trailblazer without a long and serious test drive

While I like the vehicle for its size and features, I am really unhappy with the suspension. It really rolls and sways on turns and curves. I drove a Bravada for 11 years and really was happy with its handling. I like a very stilff ride and handling.
I predominantly use the TB around town and on the highway. Because it is paid-for and I don't drive too much (retired) and plan to keep it for a long time, I am willing to spend some money to get the suspension nailed down. I don't want to raise it up, wouldn't mind lowering it some but leaving it the same height is OK.
What are the FORUM's suggestions for tightening up the suspension to reduce roll and softness?