Here is a link for a pdf with the pricing for everything, keep in mind it could go up but this is recent
https://cdn1.parksmedia.wdprapps.di.../pdf/spa/disneyaulani-laniwai-spa-pricing.pdf
I am not sure about how far in advance to book but you could give them a call and ask
The most expensive includes the use of the hydrotherapy gardens (kula wai)
And how far it needs to be booked in advance?