Pangre,

Master yourself in bunch of statistical softwares such as SAS, R, Statistica. Best would be to get certified.
I believe, you can do it within same time frame as it is required to master GRE. Why hassle much, when you have a green card.

PS: I m glad you want to do something great rather than counting breads (roti) at which most of our opportune nepali folks are lost.

Gud luck!