Wheel Bearings?

I have recently purchased a 1999 toyota camry, 4cyl, automatic. It has 183000 miles on it and for the most part it is in very good shape. The problem that I have is that there is a very present hum that gets higher in pitch as the car rolls faster. It is however independant of how fast the engine revs. It is coming from what appears to be the back end of the car. I'm a layman as far as this sort of thing, so to me it appears to be some sort of wheel thing. I work with a bunch of mechanical engineers, none of which has actually been in the car, but from my description they seem to imply that perhaps it is a bearing issue. Is this a do-it-yourselfer repair or should I take it to a pro? What could I expect to have to pay a good mechanic to do the work?

Thanks!