Megan...welcome to the Forum and the Class of 2012!
Yup, I also was a lurker in 2007 who had all the answers...just wanted to see if everyone else agreed with me. Turns out, although many did...the Camino had other plans.
As to what to do when you finish:
Since you haven't booked your tickets, consider flying "open jaw" this means you start from one city, fly into your destination...travel around a bit...then depart from another city on the way home.
Here's an example from KAYAK...they search out prices from many different travel companies:
http://www.kayak.com/?kw=kayak+airfare+ ... 2012-04-19
http://www.kayak.com/flights/IAD-LCG/20 ... 2012-04-19
In this case I landed in A Coruna in bound...but flew out of SDC back home.
No only do you eliminate backtracking, you can see other sights once you finish the Way.
In the above example, my first option (in and out of same airport) cost $1015 R/T
The second (open jaw) out of SDC was $980. In today's economy, any savings are good.
So, experiment where you want to go once you finish the Way...though the Camino is really never finished with you. An option may be traveling down thru Portugal and departing from Faro, Portugal. Gives you a chance to see more of Spain/Portugal and stay on a beach in the south.
Buen Camino
Arn