Neither the TGV nor the Thalys stop at Brussels Nord. When you get to Brussels Midi, just walk down and look at the monitors for the next non-Thalys train going north. You can ride for free the two stops to Brussels Nord. From there it's a 10-15 minute walk to the Hilton. Be careful which door you walk out of. The red light district is right next to the train station and it's kinda seedy at night.

The IC to Amsterdam leaves every hour from all 3 Brussels stations (Nord, Central and Zuid/Midi). See http://www.b-rail.be/main/index.html . The IC is cheaper than the Thalys but it doesn't have Wifi internet and it takes slightly longer. First class cars have electrical power.