The sleeper could be a fun, and often cheap, way to travel to Paris. A group of 6 can travel quite cheaply, taking a whole sleeping compartment.
Anyway, you can read about the journey here - either 6h45 by direct TGV, or the slower sleeper option.
https://www.seat61.com/trains-and-routes/paris-to-barcelona-by-train.htm
For sure a flight Barcelona-Amsterdam will be easier. Maybe fly in one direction and train in the other?
Hi Hektor. Thanks for this.
I thought it’ll be good to experience this no matter the cost / time but it’s not to be. Now time to look for flights and other ways to experience europe trains 
Happy new year!
There is no night train from Barcelona to Amsterdam (not even Barcelona to Paris). It's a possible daytime connection with one change at Paris (about 11 hours; little bit more). It's possible to go by night train part of the journey in France but it does mean a longer / slower journey with more changes (e.g. Barcelona to Latour de Carol, night train to Paris, connecting train to Amsterdam; about 21 hours travel time).
You may get prices and book your ticket for this here: https://www.sncf-connect.com/en-en/train-ticket (still too early for summer but you may enter your trip and you'll get a mail when it's available).
Amsterdam to Paris is just 3h 20min (best case) so a night train wouldn't make any sense.
Get prices here: https://www.eurostar.com/rw-en (ready to book up to July 20th).
If these are not your only trips, a railpass may make sense.
Unfortunately there are no night trains on those routes.