Sneeker, if the garage is an eye sore, and it sounds like it is, it might be best for the property value to tear it down. Not unless you wanted to put the money in and bring it back up to par.
That would be dependant on the market area. Here, in a stable market, a garage will add in value roughly half the cost of building it.A two car garage adds about $15,000 to the value of a property versus an uncovered parking area.