Prepaid option for my Canadian wife...

[calvin12]

I am posting in this forum as my question covers several different areas. My wife is Canadian and because of immigration issues into the U.S. she can not enter the U.S. and it may take several months to clear up the paperwork. She has her Samsung Instinct phone with her with service from Sprint (NYSE: S) here in the U.S. The cost is killing us and I have been searching for better options. My questions are:

1. Would we be able to replace the SIM card in her phone with a SIM card from a pre-paid provider in Canada?

2. If not, so far I have found that Fido and 7-11 (a "speak out" plan) offer the most competitive pre-paid options. Is this true or have I not been able to locate the best deal for pre-paid service in Canada?

Thanks in advance for your help/advice!