Will this sensor work without disconnecting the battery first?

You don't have to disconnect the battery to swap it out, but many techs do anyway to be safe. Either way, expect the check engine light to clear itself after a few drive cycles once the sensor reads properly.

Do I need any special tools or sealant to install this?

Basic hand tools are all you need. No special gasket material or thread sealant required—just remove the old sensor and thread in the new one. Hand-tight plus a quarter turn is standard practice.

What if the sensor doesn't fit or doesn't solve my check engine code?

Test-fit it first in good light to confirm the connector and threads match your car. If the code persists after installation, the issue may be elsewhere in the sensor circuit—get it scanned again before assuming the sensor is faulty.