Is there a contract available for pet parents to sign stating we are not liable for any damages incurred to the sitters home while she is watching our dog???

It's very thoughtful of you to consider this. Many people, (sitters & clients) don't. The damage that can happen during boarding is often unforeseeable and unpredictable for the exact reason you mentioned: The dog is in a new home with new people and new stimuli, which can include other pets and more.

If you think your dog may do well with comfort items which may include its own den to relax in, discuss what you're thinking of bringing to the sitter's home. For pets who are used to having an indoor playpen, gated space, or crate, it would likely benefit the puppy/dog to have that brought, with some unwashed bedding or linens that have the smell of home. If that's not applicable, you could still pack something with your scent (unwashed piece of clothing, toy) Also, before booking, really consider the sitter's usual schedule and the stimuli in that home and how your dog would adapt to that.

To increase peace of mind, I highly suggest a short (1 night booking) before a long trip that helps the dog adapt and builds the confidence & communication between sitter and client.