You can't snatch the Inca unfortunately but they are easy for you. Just a couple of thousand men would probably do. A good thing you could do though is to start a war and take their money. They probably have tons of gold which you could have a better need for.

I would also suggest actually that you guarantee them. Then if someone wants a piece of them they have to fight you too. You want that land and if it takes 50 years before you are ready to take it you can make sure nobody else gets it before that.

Also if you get a defensive war you have a bit lower BB for taking provinces which is always nice.
And about money and NI.. Build your economy first. You have a big enough fleet and army to keep the enemy away so make sure your economy gets the better part now. That's what I would do at least.
EDIT: And what you could wait for is for your BB to drop some more. That shortens the time you got a high BB after the peace deal.