Does this come with a bulb?

The assembly ships without a bulb installed. You'll need to source the correct halogen bulb separately—your Sentra's manual lists the exact type. Installation is straightforward once you have it on hand.

Will I need new mounting hardware to install this?

This assembly uses factory mounting points, so you're working with the existing hardware already on your vehicle. A basic socket set and screwdriver cover the install—no special fasteners required.

What if the lens gets foggy or the reflector dulls over time?

This is a sealed unit, so internal fogging or reflector degradation can't be repaired. If either occurs, the assembly will need to be replaced. That's why proper ventilation around the headlight area helps extend life.