Health insurance for relative with pre existing co (Miami)

Dear all,
I ve got an job offer in Miami. The conditions are quite good ( salary, position, ...) and even include a health insurance. They also take care of my visa query. My big concern is about my wife. Indeed she is under dialysis with a final stage of kidney failure. I heard that this pre existing condition could be a a reason of rejection for health insurance. Meanwhile, the new law Obama' care should address this issue.
Right now we are living in Qatar where everything is covered either by the government or our insurance. Does anybody could provide me information about dialysis treatment and health coverage for such disease ? Last question how easy is to apply on waiting list for a kidney transplant for a foreigner ?
Any relevant Info are welcome.
Many thanks
Cheers
Louis