The IRS will always apply payments to the oldest debt. The due date for a 1998 tax return was April 15, 2009 so that debt is not ten years old. The money they are collecting through garnishment is also being applied to the oldest debt, and that will continue. They will garnishee and levy assets until some other arrangement is worked out.
You dont have to be highly educated, but you do have to get help with things you don't understand yourself. For example, I've had a handyman at my house doing work all this week because I'm not good at that. But if I ignore it, my house would rot to the ground. Same kind of thing in your fiance's situation.

