To earn a Mechanic certificate based on experience, it's 18 months of full time work (40 hours a week) doing aircraft maintenance for either the Airframe rating or the Powerplant rating, or 30 months total, for both.
If you can find a shop that will let you fly and turn wrenches, then by all means, do so. You'll get a much broader, but less hands on and more general exposure to aviation maintenance if you go to school...I always recommend that people do, if they have the chance.
I didn't; I did mine based on experience, and prepared hard for it. I was self taught and taught on the job by doing, and I spent a year just studying for the practical test, on my own. You can do a weekend effort at Bakers or any other the other similiar courses, but you really ought to get as much experience and exposure as you can. I ended up going to work in a repair station that did everything, literally, and despite having a decade of experience turning wrenches while flying, it was still like being thrown into the fire. The learning curve was exponential...today, it still is.
Start buying tools now. Get good tools. Forget inexpensive stuff. Craftsman is okay, despite what some will tell you, but I prefer to invest in snap-on and mac...do what your budget will allow. Buy one tool at a time, pay it off, then get another. Over time, you'll have a decent set invested that will last a lifetime and be worth the investment. Get a good box (rollaway) too. Don't sell your soul like some do...I have boxes that I bought as damaged goods from Sears that have been in use for 20 and 30 years now. Still use them.
Do you have a subscription to AMT Magazine yet? No cost to you, and you should.
http://www.amtonline.com/