Please note that because of a terminal fire at FCO, things may be somewhat disorganized at the airport, and there's a pretty high risk for delays.

Regarding the airport codes, I agree that they can sometimes be confusing or appear illogical.
Don't worry about your mistake, we all make them. For example, you can go to the Air New Zealand forum and find many posts from people who want to fly to AUK (Alakanuk, Alaska) instead of AKL (Auckland).