I packed mine with grease and my fingers. If the old grease looks normal, just add some more. If it is hard, get all the old out and put the new in. One could buy one of the bearing greasers available at any auto store for ten bucks. MBs have an "infinite" adjustment on the bearing play as opposed to the rinky dink cotter pin method on most American cars. Just snug it up until there is no play, though not too tight. Then finish the six pack. Dont see how you could screw it up.
In my lifetime 48 (years) I have never had or known of anyone else having a front wheel bearing failure.