I own a tiny bit of common stock in a private company (by way of ESOs), and I have a hunch that virtually all of the rest of the stock is in preferred shares of some sort. And thus I have no idea how much my stake is worth. For all I know, it's zero.
I feel you never have as much diligence/information as an employee as a VC would who is investing in the company.
On top of that, the people with millions of dollars can hire much better lawyers and such who can truly analyze a company a lot better than your average employee.
This information should be available for all stock and option holders, including employees.
Not a lawyer or accountant, but the tax liability for one share should be minimal.
The person reviewing these statements need to know how to analyze and reconcile financial statements. Also, as shareholder, you can ask their finance person to explain/elaborate certain items in the statements.
Shareholders' Equity section of Balance Sheet statement and Cash Flow from Financing Activities section of Cash Flow statement might also give additional insights. Company will be accounting for value of preferred shares, any dividend/interest paid on preferred on these statements.
I am not sure how much an employee can push without jeopardizing the job. IME, most owners and executives of such entities are typically egomaniacs who don't like being questioned unless someone has bigger stick than them. My personal experience is very limited and only as external investor.