Once you are married and have your marriage certificate, she can apply to sponsor you for PR. There are two methods to apply, inland and outland and there is a slight difference in the processing. If you apply inland, you should commit to residing in Canada throughout your processing time. Looking at http://www.cic.gc.ca/english/information/times/perm-fc.asp at the bottom, it currently takes 12 months for first stage approval for inland and another 8 months to get PR. Those are averages. Yours could be faster or slower. Since you already have a 3 year work permit, it shouldn't be a problem for you to apply inland.
Applying outland, the processing time depends on your visa office. At http://www.cic.gc.ca/english/information/times/perm-fc.asp the first timeline for spouses says that it takes them 54 days currently to approve your sponsor. To see by visa office, check here: http://www.cic.gc.ca/english/information/times/perm/fc-spouses.asp The processing times mentioned there are for 80% of applications processed by which time so yours could be faster, or slower. It is possible if you are on a work permit in Canada to apply outland through Canada which is fairly fast but it is not common to do that and many don't about this option so sometimes Mississauga has sent people's application to their home country visa office anyway even though they asked or and were entitled to be processed in Canada.
You can find the forms here:
Inland: http://www.cic.gc.ca/english/information/applications/spouse.asp
Outland: http://www.cic.gc.ca/english/information/applications/fc.asp
You can start working on the forms now because it is a lot of info to get together such as address history etc. but you can not apply until you have your marriage certificate and police clearances may not be more than 3 months old when you apply so if you get them now, you risk that they expiry before you can apply.
