CAUTION - DANGER - BEWARE!
Read this before you start!
While this is a very easy DIY project, there is always the opportunity for you to hurt yourself or damage your appliance if you make any mistakes. If you don't feel confident in performing simple DYI homeowner tasks such as replacing a leaky faucet washer, repairing a frayed lamp cord or assembling a barstool you bought at Ikea, then this project isn't for you.
First, unplug your appliance!
Second, wear work gloves or use some other sort of thick padding (like pot-holder mittens) when handling the top metal plate (step 3). Sheet metal is heavy and can easily slice through flesh if it slips out of your hand.
You don't need to turn off the water supply unless you have to pull the appliance so far away from the wall that the hoses won't reach. Use your own judgement.
Other helpful advice:
1. You'll notice that whenever I direct you to remove something from your appliance (screws or any other part), I tell you to set it aside. I mean that literally. Take the screws or whatever, and walk to some other place at least a few feet away and set it there. This prevents you from accidentally dropping any removed parts back into the unit while the top cover is opened and its verious delicate internal parts are exposed.
2. Use a screwdriver with a magnetized tip, to help prevent you from dropping screws into the unit. If you don't have one, take your regular non-magnetized screwdriver and stroke the tip against a strong magnet. That should give your screwdriver enough magnetic cling to get you through this project.
These steps work for my model of LG washer/dryer: WM3431 (or WM3434). They may be close enough to help with similar models (if LG makes any others) but since this is the only one I have, I can't guarantee that.
If at any time you feel you're in over your head, stop and get the help of a handy friend or neighbor.
OK now that you've read all of that...