Whirlpool AC making a humming noise and stopped working?

so ive got this rather large ac unit from whirpool... 3 or more years ago, and up until this afternoon it was functioning perfectly, however at some point when i was out it seems to have stopped working and started making some sort of humming noise (the fan wont turn on now) so im just wondering if this is something i could repair myself, also i noticed that someone took out the filter at some point and got the inside filthy, and well thats all i got... any ideas woukd be nice