Bee,
I'm not sure you'll need a "tourist desk" when you land at CDG. My suggestion would be to pack along a copy of the France or Paris Guidebooks (the 2010 edition is now available, as is the London edition). The books have a LOT of valuable information that will help make your trip a lot easier and trouble free!
There are Paris Maps in the Guidebook (I usually photocopy and enlarge some to pack along), but your Hotel will have very convenient and easily read Maps available.
There are ticket office available at CDG. Were you planning to take the RER "B" from the airport into Paris? You might have a look at This Website for complete information on the transportation option to reach Paris from the airport. NOTE that the automated ticket machines at CDG will ONLY accept the newer "chip" credit cards. If you don't have one of those, you'll have to queue at the ticket office with the rest of the crowd.
If you need to buy train tickets for trips to other locations in France, visit one of the SNCF Boutiques. They're located all over Paris. Check Their Website for the details.
You can obtain the Paris Museum Pass at a number of locations in the city and at the airport. Check Their Website for all the details, including "Points of Sale".
Information on Batobus tickets should be in the Guidebook (although I haven't checked).
Good luck and happy travels!