Lately my civic has started losing power, getting increasingly worse
gas mileage, and occassionally making a rumbling noise (especially when
it's raining).  Most of my research has led me to believe that there's
a problem with my catalytic converter.  So, 2 questions:

1. For those who know far more than I do, does it sound like a CC
problem?
2. Do you know how much this costs to fix?

Being a woman in my 20s, I want to be armed with all the necessary
information when I take it to a mechanic.

THanks.