Don't know about the super fragile easy to break plastic cover, but for the spare you can just throw away the remnants of the space saver and get a real used wheel and tire cheap from another 164 and put in the trunk after taking out the plastic pieces that hold the space saver in place. There is plenty of room.
The only thing that will happen is that the floor ends up about an inch higher. No big deal in my book. Both my 164's have real spares so that I can drive the car as normal. If you would rather not do that (can't imagine why) I'm sure there are plenty of unused space saver tires laying around. I have two myself which have never seen the light of day and will be never used.