If you need to replace the side mirror on your Nissan Sentra, the cost will vary depending on a few factors. First, you'll need to decide whether you want to replace the entire mirror assembly, or just the mirror itself. Replacing the entire assembly is usually more expensive, but may be necessary if the housing is damaged. Second, you'll need to choose the right side - there are mirrors for both the driver's side and passenger's side. Finally, you'll need to select the correct model year for your Sentra. The cost of a replacement side mirror can range from $50 to $200 or more.