Cisco Routers :: Can Native VLAN Be Changed On SA520

Is PVID the same thing as "native vlan"? Can the native VLAN be changed on a SA520? Currently I believe it to be 1, I'd like to change the native VLAN to 10.
 
I have a scenario where I have a prexisting production LAN of  192.168.1.0/24 . It's a small organization (a church), but they purchased 3 Aironet 1130ag units. They want to have a "private" WLAN that is part of 192.168.1.0/24 , and a guest WLAN of a different subnet (I chose 192.168.20.0/24) . The two should never meet. There will likely never be a guest computer connected via ethernet. Guest computers would always have to connect wirelessly.
 
I left VLAN 1 on the SA520 192.168.75.0/24 subnet as default.I created a VLAN 10 , 192.168.1.0/24 subnet, and I created a VLAN 20, 192.168.20.0/24 subnet.Ports 1-3 of the SA520 are members of VLAN 1, 10, and 20 (cannot remove membership of VLAN1, which is pretty annoying).
 
Both are secured by WPA, and when I connect, the proper DHCP subnet passes from the firewall through to the wireless client, for each respective SSID.Ultimately, I'd like the SBS 2003 server to handle DHCP for VLAN 10, and have the SA520 handle DHCP for VLAN 20, but i'll take what I can get.
 
The original production LAN is connected via an unmanged switch.I'd like to trunk the unmanaged switch to Port 4 on the SA520. However, since the PVID (native vlan?) of SA520 is 1, and I cannot make Port 4 on the SA520 ony a member of VLAN 10, then anything traffic coming from the unanaged switch will automatically be tagged with VLAN1, correct? Thus causing the already existing production network to start receiving DHCP from the firewall in the 192.168.75.0/24 range.