I just checked your Beverly area for some basic information. Personally, since this is CHICAGO, and particularly with winter approaching, unless the condition of the garage is useless or unless it could be dangerous, I'd probably leave it alone. Most buyers prefer their car "sheltered" if possible.
That being said, in looking at current activity in Beverly, there are 132 houses currently for sale in that area, of which 19 are under contract. At the moment, 85 of that 132 HAVE a garage and 11 of those have contracts on them. Oddly enough, there is a slightly higher percentage of houses WITHOUT garages, and that have contracts on them today. But that doesn't take into account what areas they are in, how much below asking price those houses sold for (or if their prices were already discounted because they did not have a garage, etc.)..
Condition of the garage (or whether it exists at all) is only one element of your asking price. Right now, asking price is in great part determined by how quickly you need to sell, whether you can AFFORD to sell in today's market, the overall condition of the home....and hugely important is HOW MUCH & WHAT TYPE OF COMPETITION you have. As I mentioned, there are currently 132 homes on the market in Beverly. According to the MLS, in the past 12 months, there have been 128 sales - in other words, Beverly currently has about 12 months worth of inventory...assuming no other listings come on the market. If you want your home to sell, it must be priced AGGRESSIVELY as compared to its competition, and must be in its best possible showing condition. Today it's the best houses at the best prices that are going under contract.
Best of luck in your decision....hope all goes well for you!