When you ask about the spindle do you mean these?
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2CI0IU9072CJ01F3QG&year=1982&make=MB&model=300-DT-001&category=All&part=Steering+Knuckle

The only thing that's going to mess up the spindle is from wheel bearing failure or running in to things. I doubt you'd ever have to replace those barring some very unfortunate incident. I would highly recommend cleaning and repacking the front wheel bearings if you're planning on taking a long trip.

As far as your calipers they may not have stuck pistons but could just not be sliding back and forth correctly on the mount. Try removing the calipers, clean up the pins and mounting hardware, and re-installing them.