The Sonicwall's ports are only 100MB. Do you forsee any issues with this?
That's faster that your WAN connection. No problem.
The only issue would be if you are using the switch ports on the sonicwall to connect together Gig-E devices on your LAN. You would be limited to 100Mbps between the gig-E devices. If you do have gig-E devices on your network, put a Gig-E switch behind the sonicwall for interconnecting the gig-E devices at full speed.