I believe there are "wedges" or "tracks" that do fail in these models. I would do a search on this topic. There are many posts adressing this problem.
$500 may be money well spent if you plan on keeping the car a while. But if you could do it yourself it would be better.
1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T