20 minutes max
Mine needed a little liquid wrench to come off easily which they eventually did. If you engine compartment is similar to a 190e you might find it helpful to unclip the plastic piece surrounding the fan. This will give your wrench some wiggle room when you try to get at that last pesky nut on the radiator. not a tough job really, think all of ~50ml came out as result.
1985 190e 2.3