There are many ATMs in the arrival hall (main hall after customs). You may as well get currency in PEK.
For a taxi, just follow the signs that say "taxi" and join the queue. You pay whatever the meter says. Cost obviously depends on where you are going so we can't help on this.
No need to join a tour to see the panda. Just take a taxi or the subway. Go early before the tours arrive. The pandas are most active early in the day.