I have a 1997 Xplorer 230XL. Last year I noticed a small amount of surface rust on my low side just above the running boards in front of the rear wheel well. I used my Dremel tool to remove the rust...
One thing about rust. You can cut out the cancer and replace body panels. You cannot change the inherent design flaws that led to the rusting to begin with. It will always come back, especially on something that is nearly 20 years old.
The best product that I know of to deal with this, slow it down, is POR-15. But it has to be done before its roughed out, not after it's refinished.