Honestly, you could assign them any way you want and nobody would probably notice. However, there are common configurations that are better suited for your class/job.

As a CNJ, you want MND to make each cure that much stronger. So you would dump everything into that. No point putting into INT because you can Cleric's Stance and do the MND<->INT swap on the fly.

As for GC Seals, you get the ability to join a Grand Company somewhere around the level 20 main story mission. Once a member of the GC, you can collect seals (mainy through FATEs) as a form of currency that can be exchanged with your GC Quartermaster. Where that person is depends on which company you choose. They'll walk you through it.

The item is called "The Keepers Hymn" and it resets your points. I'm not 100% sure what rank you have to be to get it (if you can get it right out the gate or if you need to promote first) as I'm not at my console right now.