Push up and down on the front fender, if it squeaks up and down it is most likely the ball joints. +1 on the grease trick, if the joint quiets down there's your problem.

Not terribly difficult on a 124 if you have the right tools. A proper spring compressor is of utmost importance. Several members have the Klann compressor available for rent, your life isn't worth less.

Plenty of threads on the gas (and Diesel) side of the forum for the procedure.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech