No sample resumes are accessible. A competent resume writing service will provide a number of samples for review. You can assess the quality of their work only if have these samples. If there are no samples available on their website ask them for the specimens of their work. If they are unable to provide satisfactory examples of their work you had better opt for another service.
The next thing you need to do to get a searchable job-winning resume is to incorporate keywords. Resume services can help you best weave keywords throughout your overall piece. Otherwise you can match up keywords from the job ad and integrate them into your resume. Using a core competencies section in your resume writing where you list out keyword phrases is also a good idea.
To distinguish the good resume writing services from the bad ones you need to find out how they proceed with the task. A good service asks you to fill out an online question. They also set you up for an interview with the writer. This ensures that the writer is aware of all details that must be present in your resume. If a personal interview is not possible they may also provide you with other ways to get in touch with the writer.