Hi NYC Diver,
I lived in Paris for about 5 years.
The Metro/RER system in Paris is very efficient. If you don't have much luggage, it is an easy way to get into Paris. However, do be aware that if you transfer into the Metro system there may be stairs (vs. escalators & elevators) to navigate with your luggage.
The other thing to be aware of is getting through the ticket barriers of the RER. You want to put your luggage in front of you when you go through or you will get cut off (don't pull a wheelie bag through because you will get through but not the bag). There are signs and people will generally help you.
The other alternative is the Air France bus from De Gaulle. There is bus that goes from each of the terminals to the train station at Montparnasse which is in the 15e (It's Ligne 4 that goes via Gare de Lyon and on to Montparnasse). Then you would have to walk/Metro/taxi it to your final destination.
The bus can be a slightly less chaotic option especially if you are tired/in the initial jet-lag phases. Plus you get to see a bit of Paris from the bus especially between the train stations. However, I would tend to take the RER back from the center to De Gaulle because the buses can get delayed by normal traffic.
For reference, depending on where you go (and time of day), a taxi from CDG to 15e is between€60-70.
Any other questions, let me know here or in a PM
Here is the link to the Aeroports de Paris websites transport info.
Public transport - Aéroports de Paris