@Liam Goble Ok Liam, this is coming from the perspective of an Illinois attorney. Not sure on all of Pennsylvania's laws, so don't take this as "legal advice". You will need to talk to a Pennsylvania attorney to be sure. But here are my thoughts. First of all, the drunk driver who drove into your building is not going to sue you. There are no grounds (based on the facts I have read). Plaintiff's attorneys work on a contingency basis and would never take a case like that. They will take crappy cases hoping for a settlement, but never something where there is not even an argument.
So the question is, what do you do? First, I would go to your insurance company and see if they will pay for ALL of your damages. As has been suggested, you need to calculate all of your damages from this, and think long and hard about what those will be. Make your claim with your insurance company. Give them all supporting documentation. If they will reimburse you for everything, minus a deductible, take it and they will subrogate (sue in your place) against the driver to get their money, and your deductible, back. That way you don't have to go hiring an attorney and pay attorney fees.
If you cannot get a satisfactory recovery from your insurance company, then you should go get your own attorney to go after the driver for his insurance proceeds. The problem with this is an attorney is going to take a chunk of your recovery (33% in most cases but try to negotiate down to 25%). In Illinois, attorney fees are not recoverable for negligence cases. And since property damages are a fixed number, unlike injury damages where you can recover for pain and suffering, paying attorney fees means money is coming directly out of your pocket.
Having said that, if this guy really was drunk, depending on Pennsylvania law, you may be able to seek punitive damages. In that case, you can recover more than your property damages, and possibly make up for the attorney fees.
So, to summarize, try to get a full recovery from your insurer first and let them deal with litigation. If you cannot, then hire an attorney that will work on a contingent basis and ask him/her about the possibility of recovering punitive damages since the driver was drunk.