How to change loudspeaker after disassembly?

My phone was dropped into the toilet 2 weeks back but guess what I powered it on a couple of times after drying it immediately and it was flickering and didn't turn on after that. I then just left it on my desk till next day(20 hours from dropping), and it turned on and when i thought everything was fine all was bad.

The loudspeaker started making distorted(screeching) sounds after i raise volume over 25 %. Screen seems fine. But again front camera option goes missing on my camera app but rear camera is fine. I'm using android 4.3 by the way. Also, My battery life is so bad my phone restarts every time i connect the charger or even when I use it, phone automatically restarts every 5 - 10 minutes and it is really bugging me now.

I need to change my loudspeaker so i need assistance on how to do it step by step procedure wise. And I also purchased a spare battery to check if it was the battery causing all that restarting problem but it was not. Even the new spare battery situation was similar, phone restarts again and again and battery drains crazily.