1.  It’s possible.  Overnight train is probably the most comfortable ways as it’s an 8 hour trip on a day train.

2.  Try finding pricing at the French or Spanish rail websites:   www.sncf.com or www.renfe.com  I’d figure about 120 euros, including seat reservation for an adult — about 10% less if you’re 25 or under — check for lower special fares on the specific day you want to travel.

Look at the sites mentioned by Old Lady, but also get out a map and look at Bahn.de for schedules. If you’re in a big hurry and need to get from Barcelona to Paris quickly, there will be trains for that purpose.
On the other hand, if you’re not in a big rush, there are lots of potential stops to consider (depending somewhat on when you’ll travel): Collioure, Montpellier, Arles/Avignon/Orange, Lyon, Beaune, and Dijon are all very worth a few hours at least—- and that’s only one potential route. If you’d like other possible routes, repost!

thanks oldlady and basie.
 
120 euros? eekk that sounds a lot. I think i like your idea basie of stopping on different cities. I will be paying 120 some euros anyway. Why not get to see some more places on the way? i will think about that.
 
thanks again both