Is it realistically possible for a homeowner to file an "Answer" to a Lis Pendens? Or, is the only option to hire an attorney?

No. A lis pendens is not a lawsuit that can be answered. It is merely notice to the world that a lawsuit has been or is about to be filed that concerns the property.

The only option with a lis pendens is to file a motion to have it removed. You will need legal grounds to do so. That means that you need to know the legal basis for the filing, whether the filing requirements were fulfilled and some idea of the outcome of the upcoming lawsuit that forms the basis for the lis pendens. I suggest that you speak to an attorney before you take any action.