advice......sponsorship within canada,

[att]

hi

i have a question, i am really confused about the process, i got married on june 6 2006;wife ( canadian citizen) and i made the sponsorship application, we got accepted on may 17 2007 (almost a year ago) with the letter from vergreville that says the i meet the requirements to apply for permanent resident, and is mentioning something about a FINAL DECISION will be taken.

they asked me for some additional information such as police certificate from my country (mexico) and  valid passport, both were sent...my application status remains IN PROCESS.

my questions are:

how long is this gonna take, until they make de final decision, and what is that based on?

what exactly means FIRST STAGE APPROVAL?

can i get refused after the first stage approval, if that happen what else can we do?

I really appreciate any orientation in this matter, tank you so much!