i'm travelling from Paris to Frankfurt by train and I'll be dropping off a rental at the Charles DeGale airport first..should I purchase train tickets prior to arriving at the airport
Purchase train tickets as soon as you can. Prices only rise and trains sell out:
train tickets are much cheaper several months before travel and get more and more expensive up to the date of travel. So if you are traveling next week it probably doesn't matter, but if you are planning for the fall you might save a lot by booking in advance.
Note that when you drop a rental car you want a receipt that it is undamaged and gassed up; this does not happen quickly in France so I would build in a very big cushion between drop time and train time. If your train leaves from Paris factor in an extra hour to get into the city to the train station.
thanks i definitely will