Just went thru this also... Its easy to do yourself but you will need to know
which one is giving the code... there are four sensors, two in the front
(left,right side) and two in the rear (left,right side)
you'll need a 7/8 wrench, they are pretty easy to get out as they come pre-packed with anti sieze goop.
Also, the front sensors have different part numbers than the rear ones and
they cost around $100 at the dealer...
To find them just jack up the car and follow the exhaust from the head towards the back of the car... you'll see them pretty quick...