haha i am not pro lah ;p u want i can help u change but by changing, it actually voids the warranty by theory... but thats what everyone is doing... if got problem... just put back the original hardware and send for servicing... simple as that... there is no seal... so they cannot say u dismantle before :x
The warranty will only void when the user messes up some other parts of the laptop that are not categorized as user-serviceable parts/components.
Nevertheless, to upgrade memory, simply drop by Sim Lim Square, purchase memory from shops such as Best Bargain (Level 5) and request 'em to get it done for you.