bridging gateway

Hello
I have a gateway with Xfinity written on it by Comcast. if I click on "bridge" and disable wireless can I then install my Belkin N 300?
If so I assume I must change the password in my WiFi devices like my laptop and phone?
I am trying to gain a bit more security and speed instead of their gateway.
Is there anything else and is it a wise move? I assume the reverse is obvious if it doesn't work out. I hpe I do not need a signal from comcast or am doing something illegal.
Thank you

If this will help anyone,I successfully installed my router instead of the gateway router by Comcast.
Click to enable bridging then plug the printer, PC ethernet cable and an ethernet cable from gateway #1 port to the top port of your router. Then instead of 10.0.0.1 use 192.168.2.1[or ping your address- ipconfig] and use your router. Use WPA2 etc. and a password and key(written down). If I can be of help let me know and I hope this helps.
This way noone will snoop on you.