Help with coordinating train arrival in Paris, overnight hotel and then Airport train to CDG in am.

What searching have you done? Why not go from Nevers direct to CDG and stay there?

At least indicate the station where you will arrive if you want advice, rather than expecting people to look that up. And I agree that a last night in Paris beats an airport hotel unless you arrive very late at night. If your train station of arrival is nowhere near the RER B, you can take the metro to the B on the same airport ticket.

It depends on which train and which date so it could be any of these three: Gares de Bercy, Lyon and Austerlitz. When you buy tickets on SNCF Connect, opt for direct trains with no changes. Gare de Lyon has the most hotels. To get to the airport, take the RER A at the Gare de Lyon to Chatelet les Halles where you change to RER B to the airport.
There's also a RER line that runs from the Gare de Lyon to Gare du Nord where you would catch the RER B but all resources still suggest the A to the B probably because it's an easy cross-platform change.

Edit: Gare de Bercy and Gare d'Austerlitz are both within easy walking distance to Gare de Lyon. At which stations trains from Nevers arrive depends upon the date.

I'm with Janet, depending when your flight is. Lots of hotels around train stations or the ones AT CDG. I have an early flight so I'm staying at Citizen M @CDG. You also have the more expensive option of staying wherever you want and taking a taxi. SO many possibilities....A little research and you'll see what's best for you:)

It looks like most trains from Nevers come into Bercy, with a few coming into Austerlitz. If one goes into Dijon and changes, one can arrive into Gare de Lyon. (Yes I am the sucker who looked up the train possibilities.)

None of those train stations are on the RER B line, so it wouldn't be possible to walk from the arrival station to a hotel and then walk from the hotel to the RER B from the airport.

Gare de Bercy Bourgogne-Pays d'Auvergne is on the line 14, which intersects with the RER B at Chatelet;
Gare d' Austerlitz is on the line 5, which after the finish the current work in April, will allow you take it to intersect with the RER B at Gare du Nord;
Gare de Lyon is on the line 1, which intersects with the RER B at Chatelet; on the RER A, which intersects with the RER B at Chatelet ; on the RER D, which intersects with the RER B at Gare du Nord, and on the line 14, which intersects with the RER B at Chatelet.

So no matter which train you take into Paris, unless you take the TGV from Dijon to CDG, you will have to change metro / RER line at least once to get to the RER B for the airport.

One can take the TGV from Nevers to CDG with a change of trains at St Pierre de Corps.

Good idea for the evening before but a bit risky the morning of a flight, jphbucks. I take SNCF trains all the time. Way over half are late. If they had only the TGV and there were numerous choices, every hour or half hour, it would be less risky. And staying the night in Nevers, ummm, not my first choice. It's better to be in Paris or an airport hotel before an expensive flight.

Thanks everyone for your suggestions and ideas. It sounds like it may be challenging to maneuver into Paris for just the night and then out in AM for plane home, especially when we do not know the city well. It may make sense to find an airport hotel and go directly there. But if anyone else has any other ideas, we're open. Thanks again.

If you pick a hotel at Gare de Lyon, the RER A + RER B combo to the airport is super easy: the transfer at Châtelet Les Halles is just across the platform.

If you can arrive by early afternoon I would book a hotel near the RER B and then enjoy a nice dinner and evening stroll in Paris. You really don't want to eat at the airport.

What a shame to be next to one of the world's greatest cities but sleep at the airport. If you aren't sure about the transportation, just take a taxi to the airport. Your hotel can help you with that. It's a fixed-rate fare. I rarely take the RER to the airport, almost always a taxi. And if you come in by train, you have a plethora of hotels in the Gare de Lyon area.