here's how to check for correct gear mesh.
Take a peice of regular white printer paper.
Cut a strip about 1/4 inch wide x 5-6 inches long. (The paper should be as wide as the clutchbell gear)
Loosen the motor mount screws so you can slide the motor so that the clutch bell is away from the spur gear. It's a VERY important to remove the engine mounting screws and apply blue lock tite to them before you put them back in.
slide the motor to get the clutch bell gear in contact with the spur gear.
Now feed the paper in between the clutchbell gear and the spur gear.
Slide the motor over to sandwich the paper between the spur gear and the clutchbell gear and snug the motor mount screws. Turn the clutchbell with your fingers and the paper will feed in between the 2 gears. You want to be able to turn the clutch bell so that the paper ends up with a crinkle or zig-zag pattern on it, and does not tear. Fully tighten the motor mount screws and remove the paper. Feed a new strip of paper in between the 2 gears to double check it. You want that crinkle or zig zag pattern on the paper with no tears. The best way that i can think of to describe the pattern that you should have on the paper is like one of those old folding hand held paper fans that people used to use. I guess it's more of a pleated pattern.
The fit of the paper should be snug between the 2 gears, but you shouldn't feel any binding when you turn the clutchbell by hand. The truck should roll freely in the floor, and you might hear a little noise from the gears as they rotate and mesh with each other.
You may have to do this process several times before you get the feel of how to do it.
This is how I set my gear mesh on my volcano and I am still on my original spur gear (i've had my truck since jan. 2009 and have ran it a bunch).
If the gear mesh is set wrong, you will destroy the spur gear in a matter of minutes after starting the motor.

As for the steering servo making noise. I would start disconnecting the linkage one peice at a time and trying the servo after each peice is removed. If you get to a point that the servo stops making the noise, then you found the bound up part. Or, just disconnect the linkage where it connects to the servo and try the servo without the linkage on it. If the servo works fine with no noise, then start working the linkage by hand to see if you can tell where it's binding up at.
The steering linkage and the way that it's set up on these isn't the best design in my opinion, but it works good when it's not binding and able to move freely.
It might just be that there is a screw or somethign in the linkage that has been over tightened causing it to bind in a place where it needs to swivel. The servo saver may be where the snap is coming from. If the linkage is binding and the servo saver is snapping, then it's doing it's job as long as it's not broken.
Hope this helps you out.