Front Left time hum.

I have just started hearing a hum in my front drivers side wheel. Took it to my mech, and he said it may be a wheel bearing starting to go. He said there is no way to find out just drive it until it goes. So my first question is about how much should this cost?

I checked the cost of the bearing and its not that much but the labor could be. I recently changed tires, could this be the problem. Should I replace them both?

I have 180000 on the vehicle.

Thanks.