Letters arrived and installed. Original were gold and these are silver but, other than not matching the smaller 1800xr letters, they look great!
Removing the old one was easy once I figured out they were coming off in three layers. The last "adhesive" layer was a bit stubborn - I ended up using a 1" metal putty knife very carefully, followed by a little Naphtha and finished with a waxing.
Interesting, my biggest concern before starting was making sure I covered any "shadowing" from the old letters. Turned out there was essentially none. Then my biggest problem was proper placement. Eventually I saw just enough to line up the new appliques and on they went.
Note: I used a rag with just a bit of Naphtha to both press the letters in to place but also remove some residual adhesive from the surface. Now doubt dirt and crud could have accumulate otherwise.