sin card is nationwide ID, usually costs 2 weeks to get it, but you can phone them and get the number after 4 or 5 days. you can stay outside of Canada for no more than 183 days.

you should refer to application kit for how long such process takes and where to apply.

sooner or later you need to read the application kit carefully, so why not do it now, then ask questions. This can help you get correct answers in a much better and faster way.