I agree with Pete. 10 years isn't long at all. I am an AC tech and it could be something as simple as a relay switch and a charge of freon, which will run you way less than a replacement. Check the relay switch. This doesn't cost more than $50.
Check for a freon charge first. If good, check the relay switch, on the unit. When your system is switched on, it sends approx 24 volts to a switch in the unit called a relay. This activates the AC in turn activating approx. 120/220 v to kick your fan on cycling your unit to start the compressor. If your relay is not recieving this voltage from your thermostat it will not turn the fan on, and the compressor will not start. If your relay is good, I would then check the thermostat. They tend to be changed more often, and are inexpensive. Compared to a new unit, these are the steps to take. Once your fan is operating, so is your compressor. Then you can see if the air is cold.
J-Daddyshammer