How to open a router case

[pedruid]

I have a ZyXEL IAS P2602 WiFi Router whcich was supplied with a Telkom Contract 4.5 years ago. I can no longer get a WiFi signal to my laptop or Kindle and want ot open up the case to see if I can rectify the problem.
Anyone got any idea how I can go about this?
Should I forget it and go for a new WiFi Router? If so what make and Model?

 

[T-Man]

The screws are usually hidden behind the rubber feet.

4.5 years?? - may it's time for a new 300N Wifi Router.

 

[pedruid]

What make is a 300N and how much does it cost?