One additional tip: set up a bucket under the filter trap housing (say, in the utility drawer underneath the washer) before you open it up, lest ye piddle water all over the floor.
You'll need to unseat the filter/pump assembly and then tip it forward to allow the water to clear the floor of the washer chassis. On the HE3t, it's secured to the chassis floor with one T20 screw.
No need to disconnect the hoses or plugs; there's enough slack to keep everything connected.
Remove the screw, slide the assembly forward out of its mount, then tip it down a little. (There's a bunch of wires in a plastic frame running laterally in front of the pump/trap assembly. But don't worry: you already unplugged the power cord, right?) Unscrew the trap cover a little (Don't remove it completely!) and let the water out. Tighten it back up to stop the flow so you can empty your bucket. (Ours took three or four trips to the slop sink to drain all the way.)
When it's empty, remove the cap and clean out the trap. (Our trophy: one very old, very nasty facecloth.)
Slide the pump/trap assembly back into its mount, replace the T20 screw and the lower front panel, and you should be back in the laundry business.