Every battle-hardened professional Appliantologist has his favorite technique for replacing the door gasket (also called the "boot" or "bellows") on front load washers. Although the door gasket on all makes of front loaders are very similar in construction, there are enough differences among the brands that certain techniques work better on some brands than on others. For example, many Appliantologists prefer to replace the door gasket on a Whirlpool Duet washer without removing the entire front panel of the machine.
Although the door gasket on LG washers is very similar to all the rest, that inner retaining spring seems to be just tight enough that it's worth the extra effort of removing the front panel to facilitate the installation. LG also makes two special spring pliers to help with removing and reinstalling the outer and inner retaining springs. Most Appliantologists say they can get by without the outer spring clamp tool Part number: AP4438623
but that inner spring clamp tool Part number: AP4439038
The other big thing to watch out for with getting the replacement LG door boot is to check to see if the model you're working on has the extra drain port at the 6 o'clock position or not. Sometimes, even looking up the door boot by model number will give you the wrong replacement boot and the presence or absence of the drain port seems to be the key difference.
Here's a video that shows how to replace the door boot using both the outer and inner spring clamp pliers and by removing the front panel of the machine.