Originally Posted by ScottGem
First thing is to get copies of your returns. Did the G/F sign as a preparer? if so, you can sue her for the money she never paid. Not so much to collect but to show the IRS that you did give her the money.
Next, go to the IRS, before they come after you, and explain to them what happened and ask what you need to do now. As long as you approach them, and considering the small amounts, they should be willing to work with you, maybe even waiving penalties.
As far as the 401k is concerned, you will have to add the outstanding loan balance as income and you also have to pay a 10% penalty (more bad planning, you should have paid off the loan and rolled it over to your new job, then taken a new loan out).
I would also get a proefessional preparer to help prepare your returns this year.