student visas info

Hello, I would like to have some advice on student visas. I would like to move to Australia from Canada but if the new SMP won't have my occupation (mdical laboratory officer) on any of the states lists I won't be able to apply for a 176 State sponsored PR visa as I was planning.
So I am now thinking to go another way, with a student visa. I would like to know the following:
1. How long would it take to get a student visa?Can I apply at any age?(I'm in my 30's)
2. Can I study in any field or is it for only some specific university programs. If yes, which ones?
3. I don't want to study for a long period of time, so what are some programs that would enable me to get a visa that are only 1 or 2 years long
4. What do you suggest I study?I am interested in the science/medical field

Any other info or advice on this subject would be appreciated.
Thank you!