The MB manual has specific torque value for tighten the bearing, by mean of using a dail gauge. When I replaced the front rotors on my 115, I felt the same shimmy, and required to re-tighten the bearing.
The brass V-shape spring is the contract spring. I think it is for the radio. They are cheap, less on dollar. I can't remember if it is on the 140, but I am sure it is on the 123 and 124 models.