How do I answer a complaint for modification of child custody?

Question Details:

I have been divorced since April of 2008. I have joint custody but I was recently served papers where my ex-husband wants full custody. I am currently residing in Texas and he is residing in SC. I cannot afford an attorney but would like to answer his complaint as professionally as possible. Are there forms that outline how to do this? I do not want the current custody status to change. P Important Notice