Ideally, you would take the cold air off the floor area as far away from the heat inlet as possible, and having the return come back to the wood stove, but actually anywhere out the sidewall would work. You are pumping air in, and for the air to flow properly, you need to provide a place for equal amount of air to escape or exit the building...otherwise you are sort of creating a balloon with no place for the heated air to go, and back pressure preventing it from gett'n into the garage.
What Mezz is talking about is that there are ordinances against wood smoke nowadays, and since the stove will be outside, (coincidently where the wood pile is) you need to at least put some sort of roof over the stove to prevent rain and snow gettin on it, unless you are spending the big bucks and buying an outdoor stove.
Just a set of 4 by 4 poles on 4 corners with support 2x4's going between them, and perhaps a cheap metal roof with left over metal roofing from somebodies roofing job would work. Stove pipe thru the roof. If it leaks a bit to the stove it won't hurt it much if you keep fire in it. Off season, need to prevent rain from rusting it.
Otherwise there is no reason you could not do what you want to do. Remember every turn of the air pipe restricts the flow of the blower. Straight is best if possible.
Snap a pic when you're done and post it up....sort of curious how this will turn out for you.
