My advice...don't use a furnace or window company to clean your chimney. Especially if you don't know what's up there. All they will do is stick a vacuum up it.
I actually used to work for this company...they specialize in this work. One of the oldest in Calgary.
Clean Sweep Property Services
403-640-4240
They will use the proper brushes/brooms and clean-up methods.
You are wise to get this done. It used to blow my mind how dangerous some of these chimney/fire place combos used to be.