I know a bit about LP12s, but I'm not an expert...
No idea about the St. Louis area. But--stating the obvious--you might check with Linn to see if there is a dealer near you. You might also check to see if there are other audio dealers in the area who can work on Linn--I've known of audio dealers who don't sell Linn, but have someone on the staff who knows about LP12s. Sometimes, I hear, these non-Linn dealers actually do a better job than the official dealer.
The turntable probably also should have the bearing oil changed and have the suspension checked.