Yes, Welcome to the board!
1st thing I'd check, is to see if the statute of limitations ran out in regards to being able to bring a suit against you. In California it is 4 years from the date of the first missed payment.
If the statute of limitations has expired, you don't have to send in a cent and you don't have to reply to anything.
Other than that, start reading the threads here, all that you can. I also recommend reading items in the download section on this site.
This site has TONS of good reading too;
wealth4freedom.com
Bless you MORE in Jesus' name!