That is where I have mine.......in the garage.
My setup is a framed wall that I go through. Hence the triple wall pipe through the wall.
If you have a block wall, you should not need the triple wall to pass through. Unless you have it lined on the inside with something else. Or some type of covering on the exterior.
I come out of the stove with an elbow then up straight for about 8' then through the wall. The pipe comes out through the wall into a "T" which is capped off on the bottom leg. The upper part extends up about 24"-36" and then has a cap on it.
The only way to be sure is to hook up a manometer to it to check the draft.
HOWEVER AND THIS IS VERY IMPORTANT THEREFORE THE CAPS....YOU MENTIONED INSTALLING THIS IN A GARAGE. BE VERY CAREFUL OF GAS FUMES !!!!
There may be some restrictions from your insurance company. So it is best to make sure you are covered. In fact you may wish to first mount the stove on a couple of cement blocks to raise its level. Gas fumes are heavier that air and will lay low to the floor.
I have removed all gas cans and any thing similar from the garage prior to starting the stove each season. I once had a scare when the generator fuel tank sprung a leak while in the garage. I quickly removed the generator and opened the doors to allow the fumes to escape. I hate loud noises !!!!!!
Post any other questions you have. If I get a chance, I'll take a pic and show you my setup.