You never did answer why you want to do this.
Here's a video on how to remove/replace it: http://www.youtube.com/watch?v=_UUukT1FOew
It doesn't look overly hard, but if you don't feel comfortable doing it, there's no shame in asking or paying for help to get it done rather than breaking it beyond repair.
Replacement keyboard available here:
http://www.amazon.com/keyboard-Emachines-Series-Laptop-Notebook/dp/B00468F9GC/ref=sr_1_2?ie=UTF8&qid=1342960024&sr=8-2&keywords=emachines+E725+replacement+keyboard
(Maybe cheaper on eBay)
From what I can see on different pictures of the keyboard, it isn't clear whether the keys pop off or not. If they do, usually you can slip your fingernails under two opposite sides and lift up and it will come off. If it doesn't come off with a moderate amount of pressure, then you may be better off having a professional look at it, or just replace the whole keyboard for less than $20US.
SC Tom