You will need an old credit card, smallish hammer and a thin screwdriver. First slide the credit card under the edge of the emblem. Next slide the screwdriver between the credit card and the emblem. This will keep the screwdriver from scratching your paint. Now you need to pry upwards carefully. It is a good idea to clean the area under the emblem, as it hasn’t seen the light of day for eons. I like to wax the area to protect it from the elements. Next replace the grommets. Pry the old grommets out.
The new grommets install easiest with a LIGHT tap of a smallish hammer to seat them. The emblem can now be pushed into the new grommets. It is a good idea to only apply pressure with your thumbs directly over the studs. If you press to hard on the center it will distort. Z3’s, X3’s, X5’s and a few other models have the rear emblem glued on with doublestick tape and the two studs. These take a little more effort to remove. You also want to remove all the old tape residue to make sure the new emblem is level and adheres well.
...read the full guide with pics here