An all-in-one mobile wellsite service unit for providing equipment and services at an oil and gas well related to well abandonment is provided. The mobile unit comprises a water storage tank, at least one cement mixing barrel for mixing a cement slurry, a progressive cavity pump for pumping the cement slurry, and a hydraulic hose for connecting to a hydraulic power source to provide power to the cement mixing barrel and the progressive cavity pump. The mobile unit may also contain downhole tools needed for well abandonment, including a well cleaning tool, a cementing tool, a hydraulic packer, and more.