2 short days in Provence

Not too crazy. The first direct TGV of a Sunday leave Paris about 7:15 and arrives in Avignon at 10:00. Buy reserved train tickets in advance for the best fares.

Sunday
Morning TGV to Avignon (2hr 39min)
Afternoon to Nimes - Pont du Gard http://www.pontdugard.fr/en/practical-information
Monday
Morning to Arles
Afternoon in Avignon - Palais des Papes http://www.palais-des-papes.com/en/content/practical-infos
Evening TGV to Paris

I second David's recommendation. We recently stayed in Avignon and loved it. Visited those sites he mentioned, plus Senanque Abbey to see the lavendar, and the lovely village of Roussillon. All wonderful.

We had a whole two nights in Avignon area a few years ago. That gave us a whole day to see a few things. We had hoped for about a day and a half, but I messed up buying train tickets in Nice and ended up getting tickets for the slow train instead of the fast train, and a tremendous rain/thunderstorm delayed the slow train leaving Nice even more - by about 90 min, so we ended up arriving about 3 hrs later than planned.

We had a tour booked for the afternoon that took us to Pont du Gard, Nimes and Uzes (and it wasn't nearly long enough - only about an hour at each spot - and it went fast - but it gave us a taste). I will say in the morning we did the Pope's Palace in Avignon - I wish I had seen what other people said about the palace and that we had spent more time wandering Avignon...it was OK, but was mostly empty and not terribly exciting (and for the price...). The Pont du Avignon was interesting (Pont St Benezet).

What you have described is doable, but from my experience things just move more slowly in Provence and you will want to linger. Try to go on Saturday evening and stay in Avignon if at all possible, even if you get there late. Find a hotel downtown that is an easy walk to the Palace of the Popes. That site will take longer than you expect, but you can easily walk to the Avignon Bridge from there. If Saturday is not possible, consider renting a car at the TGV station when you arrive in Avignon on Sunday. Book the car before you leave home for the best price. Hertz in there as is Sixt, a German company who has opened a number of offices in Florida in the last few years, and any of which can help you book in France. I've used them in Scotland and Provence and they were great. You should get a Michelin map of France in Rick's travel store and you'll have no problem getting around. After you get the car head west over to the Pont du Gard, then from there go south to Nimes and/or Arles, staying in either of those for the night. On Monday get up early and visit the one where you didn't stay, then drive back to the TGV station, turn in your rental car and take either a taxi or shuttle to the town center. Go to the Palace, the bridge and anywhere else you can squeeze in and go back to the TGV station the same way you came. That prevents the hassle of driving and parking in Avignon and leaving time to turn in the car. The terminal is new and modern with food and the latest electronic schedule boards, but you should give yourself an hour there to be comfortable with the platforms and to ask for help if you need it. The trains are not in the station long and you need to be ready to board when they arrive. Make lots of notes of things you DON'T get to do for I'm certain once you're there you will absolutely want to go back for the full treatment. That takes a week or two....or longer.

Since u only have 2 days i strongly suggest u take a bus tour from Paris for your visit or from avignon once u arrive.
The train travel alone will take lotsa time. Best to have a guide take u to see the highlights espec since u are going solo. Logistics can be overwelming for getting around once u are there.
Itbwill be euros well spent. Provence is beautiful.