If you are set on not having someone look at it, at least take a look at your condensation line. It will be a PVC pipe coming off your inside unit and going to a drain. It probaby also has a u-shaped trap so that it can operate under negative pressure.
The issue is that algae can build up over time and cause water to back up and drain in places you don't want. A service person doing a tune up would take of this task... But at a price higher than what you'd want to pay.