I'm not sure if you are asking for an appraisal of this property, or if you want to know what it would sell for in today's real estate market.
Either way, there is a lot of investigation that needs to be done in order to properly answer this question. If you want an appraised value, you need to contact a licensed Real Estate Appraiser, familiar with the Sebastopol market, and country property. If you want to know what the property would sell for, then a local Realtor would be able to perform a comprehensive market analysis of the property, and it's improvements, and arrive at a price they think it would sell for in today's market.
Please let me know if I can be of further assistance, or answer any additional questions.