iPad 2 iOS update not working
Unfortunately, Apple do not officially support iOS 8 on the original iPad (or, as you refer to it, iPad 1). This screenshot of the "iOS 8 is compatible with" section does not list your device:


It is strange that your device is trying to update to an iOS version beyond the maximum of 5.1.1:



It is one of three things:


A bug in the update software;
Your iPad is in fact a later iPad, or;
You are not running iOS 8


Could you provide a screenshot of your General > About screen,



to see both what iOS you are indeed running, and which device you have. Also, a screenshot of the Software Update page would be interesting.

 You can take a screen shot by holding down both the home and power buttons simultaneously.

You say that your icons are similar to those on iPhone. Have you jailbroken the iPad at all..?

Instead of trying to update over the wifi, which can cause memory issues, connect it to a Mac or PC and try updating via iTunes.