Do these caps seal properly with the vented cut outs?

Yes. The vents are positioned to allow pressure equalization and moisture escape while the cap seals at the valve stem. They're designed for function and appearance together.

Will these fit my current valve stems without modification?

These are standard hex cap replacements. Test-fit on your valve stems before final install to confirm thread compatibility—stem designs vary by engine.

Do I need to polish or maintain the silver finish?

The silver finish is durable as-shipped. You can hand-polish with a microfiber cloth for extra shine, but regular engine bay washing keeps them clean without special care.