Father Died, His Corporation Has No Employees Now, But Owes $ To Irs

My father recently passed, he was a Realtor/realestate agent who has had his own corporation for decades. He has employed a small number over the years but since his health declined a few years ago he has been the only "employee?" of his company. There is no known "corporate plan" or anything, I have never worked for it. He had set up a trust for his personal stuff for which I am the trustee, but doesn't specify any corporate things except a general "I can made business decisions if he is incapable"

As far as I can tell his business assets are only a $4000 checking account and a $800 printer. Office furniture was mostly junk. His car may be owned by the business too but I can't find the title (looking in to). I do not have access to the account because only he is listed on it with no beneficiaries.

I found stacks of mail showing the business owes taxes from years past that have now gone to collections, about $17,000. I called the collections agency to see if those were still owed as he sometimes pays balances but keeps the bills ????. They were unable to give me any information as I am not part of the corporation and there's no business succesion plan specifically.

My worry is that as "trustee/executor" of the estate if I don't clear this up collections could come for the estate (me?) and for his personal assets. We have enough from his retirement accounts to cover that debt but I don't know how to navigate it.