Edit: I should said this first: One way to see if its the motor would be to turn off the AC for a while to let the motor cool down. Then, start the AC. If the motor turns momentarily but eventually stops then it's 90% certain that the motor has some shorted windings. This happened to us about 6 years ago. I was 17 and I was able to track down a motor and replace it. If you're willing and feel confident in your ability to do this yourself, call up an electrical motor place and see if they can match the model #/specs of the motor. Any HVAC place will just try and get you to pay them to come out.
I think the motor cost about 160$ CAD after taxes (14%) - it was a 1/6HP, 240V capacitor start motor which replaced a 1/12HP motor. The shaft of the new motor was about 5" long and I had to cut it to a proper length with a hacksaw.
Also, check if the screws for the breakers feeding the AC fan motor are tight. Repeated temperature cycling can cause those screws to back out. This happened to our dryer about 5 years ago. If they're loose, turn off the breaker and tighten the screw.