Thank you for contacting Intel.
As of the moment, we do not have firmware update for Intel X520 Series Retail Card as we do not encounter issues with it. The firmware update from Dell* is to fix some issues with the affected adapter models.
Hope I was able to address your concern.
We do not have firmware update for X540-T2.
With regards to RMA, If it is an OEM Dell X540-T2, you may contact Dell* for warranty support. If it is an Intel retail version X540-T2, the warranty is limited lifetime, you may refer to the link for reference: Limited Lifetime Hardware Warranty for Network and I O
You may contact the Intel Customer Support to assist with the replacement if needed.
Here is the link for contact info, please choose your location to locate the support in your area : Contact Support