As long as you keep it covered when not in use you should be OK in the garage. Remember that you will need room on both sides for the tray to feed in and out. Also, as with most quilting tasks, the height that the machine sits will affect your usage. I would try it on the kitchen counter and also on a dining table to see what height works well. You didn't say if your fabulous gift included extra cutting mats. If not, you might want to look into getting some extras to have on hand. Think of the mats as consumables, like rotary blades. You can extend the life of your cutting mat greatly by using both sides, and flipping the mat end for end etc. The quickest way to wear out a mat is to cut the exact same shape in the exact same spot. You can mark the die on the rubber side with a metallic sharpie (I like silver). I make a mark where the blades end so I can quickly and accurately place the fabric. For the best cuts, treat your fabric the same way you would do for rotary cutting. Press it, and if you starch or size your fabric now, continue to do so.
And finally, Ebony, at love bug studio, has a lot of info on her blog and also some great you tube videos.
http://www.lovebugstudios.com/fabric-die-cutting/