The proficiency exam will be similar to a final exam, but shorter (2 hours). Final exam review materials can be found on the Exams subpages for previous offerings of 173.
You can't get proficiency credit if you have taken the the course already. Low grades can only be repaired by retaking the class.
If you have taken too many courses that are supposed to follow 173, you also can't get proficiency credit. However, you can take the proficiency exam to get exempted from the requirement to complete 173. Please warn me if you may be in this position, so we can consult with the CS academic office about the administrative details.
If you are interested in taking the exam, email the instructor so we know how many people to expect. Also, remember to bring a photo ID (e.g. university ID, driver's license) to the exam.