Just got back from France (Brittany) and took the TGV r/t from Paris. They don't announce the track very long ahead of time, so just stay by the reader board and keep an eye out for the train number and destination. Don't forget to punch your ticket (compostez) in the little yellow stand on the way to the platform. Finally, pay attention to what train car (voiture) you are in- you have to walk along the length of the train on the platform until you find it. Murphy's Law says it will be the furthest away, especially if you have a lot of luggage. Pro tip: don't have a lot of luggage! Especially with Airbnb's if you select ones with a washer.
Check out the Ouigo trains which are cheaper.
We also visited Provence in February (2010). We stayed in Avignon, it was cool. Aix might be a little more alive in the winter though, since I believe it is a college town. We did manage to get out into smaller towns on the bus, but we would have likely wasted less time with a car- the winter buses are few and far between. Cote d'Azur was easy to do by train since we just visited the coastal towns and didn't go inland.
FYI, Menton, on the coast next to Italy, has a cool citrus festival in February. Oh, the limoncello, yum....