I then assume you are also shareholder? Then regardless of the resignation, you still have an issue, even though it's a C corp. Yes you need a lawyer/Tax Accountant.
Question is, how bad do you want your money from the Partner? Resign, sell your stock to the partner for the amount you are owed (ONLY WAY YOU are totally free and clear of the Corp UNLESS you personally guaranteed anything - better check!) and have the partner sign a personal note for it (the stock) - that way you have broken the 'corporate veil', and if the partner doesn't pay you by the terms of the personal note, you could take action against the partner for the balance. However, in most instances such as this, unless something big happens, the Partner will eventually fail, and he will file BK (you lose) or you will have to sue him for it (you still lose).
It may be that the business can make money by cutting out the payroll/costs for two owners vs. one - and maybe then the partner could pay you some of what you are owed via the note. You might get lucky but the odds are certainly against it.
Best of luck