I can do you one better, I can actually recommend two auto shops that I personally trust very much. They are both in Saint Charles county, but if you're anywhere in the St. Louis metro area, either is worth the trip.
I've done business with both over the years and they are both extremely honest and fair. Tell them Mark Nahrgang sent you.
1) HiTech Automotive in Saint Peters. 150 Boone Hills Dr
Saint Charles, MO 63303
(636) 928-6050
2) JC Car Care (2 locations)
JC Car Care South
1408 Harvestowne Ind
St. Charles, MO 63304
636-928-5150
JC Car Care - North
135 N. Kingshighway
St. Charles MO 63301
Phone: 636-946-5707