You don't have $60 ? http://www.amazon.com/D-Link-EasySmart-Gigabit-Ethernet-DGS-1100-08/dp/B008ABLU2I/
Bridging the pfSense interfaces will be:
1. More complicated
2. Exhibit inferior performance
Yes, it can be done, but to be frank, I'm not sure I have the patience to spend a bunch of time talking you through doing it wrong so you can avoid spending $60.
https://doc.pfsense.org/index.php/Interface_Bridges
Here it is in a nutshell, though:
Create VLANs 100 and 200 on eth1 (or whatever your available interface is)
Create a bridge containing LAN and eth1_vlan100.
Assign interface LAN to BRIDGE0.
Assign interface GUEST to eth1_vlan200
Set your guest IP info and firewall rules on the GUEST interface.
Your AP should be set to send your internal SSID tagged on VLAN 100 and your guest SSID tagged on VLAN 200.