1. Can't really say how long it will take without knowing what embassy would be reviewing your application. Here is the link for average processing times.
http://www.cic.gc.ca/english/information/times/international/05-fc-spouses.aspIf you plan to start studying in September, that's a pretty short time frame and it might not be finished in time. Keep in mind that you have to show proof of resettlement in Canada to be eligible.
2. If you work outside of the country after you finish your studies, your wife's PR status is fine as long as she is with you. I don't know how the renewal process works from outside of Canada but maybe a member who does will comment on that.
3. Yes, as a PR your wife can sponsor her parents and you will co-sign the application. Unless they fall within another category of the economic classes (i.e. skilled worker, etc.) there is no faster way to make it happen and it takes a long time. The average processing time is two fold. First, the sponsorship application must be approved in Canada. Please see this website:
http://www.cic.gc.ca/english/information/times/canada/process-in.asp#sponsorshipThen the file will be forwarded to the appropriate visa office where the processing times are listed on this website:
http://www.cic.gc.ca/english/information/times/international/08-fc-parents.aspSo add the two together to get a guesstimate of how long it will take. These processing times are subject to change without notice.
Hope that helps a little.