Gas and Oil Home Heating Furnaces - Central AC tripping breaker

I installed an Amana 2 and a half ton central air unit about 12 years ago with the A coil in the furnace plenum. Kept up with the cleaning of coils and changing filters on it and never had a problem. Came home tonight after being away for the weekend and the house was hot and i checked the breaker and it was tripped. I reset it and it just tripped again. What can i look for that wouldn't be too hard to fix or do you think i'm looking at getting a new compressor?
thanks for your help.
Joe.

I assume you mean it trips immediately like when there is an electrical short?? Well, any one of the electrical components could be faulty. Starting at the switch at the outdoor unit, look inside for any burnt wires. Take the cover off the a/c unit and look around, See any burnt wires? Does the capacitor look bulged out, blown or is it leaking oil? Locate the terminal box on the compressor and remove the cover. Any burnt wires/terminals in there? Look at the contactor- [a big relay looking thing] any ants/critters on the contact points. Is it pulled in? With the power off, make a sketch of which wire goes to which compressor terminal. Remove the wires and tape up the ends pretty good. Now, restore power. Breaker still trips or not? If no, it's the compressor. If yes, remove the wires for the fan motor [again make that sketch] and try again. Keep eliminating components until the breaker quits tripping. Don't rule out the possibility that you might have a bad breaker. Let us know what you find.