I'm taking a night train from Toulouse to Paris that arrives at Gare d'Austerlitz at 7 am. I am planning to book the 8:25 am Thalys train to Amsterdam that leaves from Gare du Nord. Should that be enough connection time? I don't recall the Metro taking that long to go 5-6 stops (I think) but want to be sure. Also, if I miss the 8:25 am train, can anyone tell me how difficult it might be to exchange, assuming there are seats on the 10:25 train? I'm traveling the 2nd week of July so I'm in the middle of the season. Thanks.
That should be reasonable connection time if arrival at Austerlitz is on time and nothing goes wrong. Your easiest means of travel is Metro Line 5: the Line 5 platforms are up in the roof of the station (yes, literally). Also make sure you have enough coins to buy Metro tickets from a machine at Austerlitz. Ticket exchange: depends on what type of ticket. Full-fare tickets should be exchangeable but cheaper ones may well be limited to that train only.
Thanks so much. I'll go with that plan and keep my fingers crossed.