Assuming you found the right official file, proceed like a careful minor: read the release notes, back up your current settings, and avoid power interruptions mid-flash. Many routers give an option to save and restore configuration — use it. If the release notes mention a full reset requirement, expect to reconfigure PPPoE, VLANs, or custom DNS afterward. If you’re not comfortable with re-entering those details, schedule the update when you can spend ten to thirty minutes troubleshooting.