sprint sero data plan needed?

i have sprint sero 500 which includes free unlimited internet,to get a Palm Pre and some other phones im being told i must upgrade my plan to data plus unlimited,i got 2 questions,first is there a way to get that for free?2)will the phones internet work with a simple internet plan?

I hvae that plan and I am using the Mogul. That plan should already have unlimited data.

I think you answered your own question:
To use the Instinct, you must upgrade...
(The upgraded plan includes internet for the Instinct)