OVM, at 290k I can guarantee you they aren't in good shape. The stock Sprinter shocks are designed for 50,000 mile lifetime. They haven't failed utterly (as in collapsed), but if you (when you) replace those shocks, your butt won't believe it's the same vehicle. Because of all the highway driving we do, it's realistic to expect 75,000 miles out of the stock shocks. Shocks is one of those things that start to go back the minute you put them on, and they go bad very, very gradually (usually), so you don't feel it. Most shocks (Monroe, the OEM's,) should be replaced about every 50,000 miles. I think Monroe recommends that, or 60,000. RLENT will know for sure.
There's a post by me here somewhere about the before and after with the Koni shocks and the heavy duty swaybar.
I replaced mine with Koni's because it's basically one time shot and over the life of the van they cost less, and perform better, than replacing the shocks with OEM or cheaper shocks more often.
