The wireless key can certainly be changed, along with the encryption. You can log into the router at http://192.168.1.1/ with the following username and password sequence:
Username: admin
Password: This is the router's Serial number on the printed label.
Once in, just click Wireless Settings. I *STRONGLY* recommend using WPA2-PSK AES as your Encryption over WEP or mixed WPA/WPA2 mode. You'll get better performance, and especially with Apple devices, things will just play better.