If that's what you want, it's not hard.
Go to the Build Game dialogue, and then the Level Settings tab. Now, go to "Level Settings", and
take out the path to everything that is relevant. In other words, take out the Health and Lives image and numerics, the Guns and Ammo image and numerics, and the Crosshair image.
Once all of those paths are gone, change something else (for some reason, it never saves the last thing you changed)--I usually change the number for the fog colors, since fog doesn't work anyway.
And you may want to take note (write down) the paths of each thing, in case you want to put them back later.
Evil has a new name. Demo out now!