ball joints? they are on the control arms, it's what your front wheels pivot on I believe, you can press the old ones out and new ones in. As to the difficulty I dont know I had mine done as I dont have the tools to do it, there's a test to see if they are shot, I'm not sure of the procedure someone else will chime in

__________________
hum.....
1987 300TD 311,000M Stolen. Presumed destroyed