The 'stripped' portion is in your case I believe a trimmed part since threading there would serve little if any purpose.
The 'lip' is indeed a removeable part. You can do a fine job at repacking without taking it out, though it is better if you can. With one little catch. It is easy to warp the part if it isnt removed propperly. Usually the method that works is to find a screwdriver or a dowel than matches the hole diameter then inserting it and rocking back and forth lightly. It should pop out. Make note of which way it goes(its remarkable how one can forget). Repacking is much easier that way. Put it back on with a soft block(wood or the like) and a light hammer.
Hope that helps.