As long as the spring is still in good shape, no problem with just replacing the shock. This is going to be a one-time expense (more than likely) so I would probably opt for the more expensive Bilsteins. You might call around and see if you can find a better price than the $157.00 you quoted...boy, that sounds high !

How many miles do you have on your ML ? If less than 100K, definately shocks only. More than that and the springs are probably sagging a little and replacement will help with the ride.

My ML had 225K when I changed mine out and some of us hit a particularly good deal on the Sachs combo.Whatever you decide as far as parts, consider doing the labor yourself. That's at least equal to the cost of parts.

Plenty of advice on this site and others regarding the swap. Good luck !! If the fronts are still original why don't you change them out with the Bilsteins..about 100 bucks each and go from there. You really should consider doing both axles....