If it didn't happen due to your own negligence, I'd recommend talking to your employer (or whoever owns the building) about taking care of it before doing anything. Go ahead and get a quote from wherever you'd usually take it, and press them if necessary on their responsibility for the damage.
A coworker had the windshield, hood, and front fender damaged on his 3-series after a 2-inch piece of our relatively-new parking garage fell on it while parked. Our employers first response was that it was his risk by parking there. They reversed that decision pretty quickly when he had a more senior manager look into it.
Whether you get someone else to pay for it or not, I'd personally get it taken care of professionally.
Good luck!