Sprint : How Do I Update the Software on My Sprint SPH-d720 (Nexus S 4G) Mobile Device to GWK74?

Samsung has released a software update for the SPH-d720 Nexus S™ 4G. If your current software version is GRJ90, you will receive a network notification for the GWK74 software update. The update process will be performed OTA (Over the Air). It may take several minutes to complete.

Software Update (GWK74) Details

Google Security Fixes
Google Wallet
Check the Software Version on Your Mobile Device

Press the Home button > Menu button .
Touch Settings > About phone
The Build number shows the current software version on your mobile device.
Note: If your current software version is GRJ90, you will receive a network notification for the GWK74 software update.