A humming sound coming from the drivetrain when teh car is in motion is usually due to a worn wheel bearing just as you suspect. Another sign that it is a wheel bearing would be if the noise changes in intensity when steering the vehicle around curves at highway speed. As you steer side to side you shift some of the vehicle's weight side to side as well, loading and unloading the worn bearing. If the noise changes when steering, the bad bearing is on he side towards the outside of the curve when the noise is loudest.
The wheel bearing on this model is serviced as part of a hub assembly; this is the wheel bearing, Antilock brake wheel speed sensor, and the part that contains the wheel studs all in one piece. Wheel bearings are not serviced as separate parts on this design, because of the very tight internal tolerances required in this type of design.
Repair cost can very somewhat according to the brand and quality of the repair parts used, the skill of the technician perfroming the repair, and prevailing labor rates in your area of the country.
A genuine GM front hub assembly costs $274.92 for the part.
Labor time required is 1.1 hours (multiply by the shop's hourly labor rate for the dollar cost for labor).
THere are cheaper hub assemblies available from parts stores, but often times the quality leaves much to be desired; especially if it is from a discount store like Autozone or Advance. Discount stores compete aggressively on price alone, and buy their parts from the absolute cheapest overseas suppliers they can fiind. As a result the parts they sell often do not meet manufacturers specifications and frequently fail after a short time in use.
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