Next you will need to remove the inner part that the LED inserts into from the smoked plastic lens.
The 2 pieces are held together simply by way of the clear/white lens from the inner piece snapping into the cutout of the smoked lens. You'll need to apply a significant amount of outward pressure to allow for room for the parts to come free from one another. You may find it helpful here to use a small blade or knife to assist in prying. But this is where you also want to be very careful NOT to break something! It's a careful balance, and takes some wiggling. I used more pressure than I thought would really be safe, and that's just what it took for me. Remember that these parts have been stuck together for 20 years or more and they'll need some patience to come apart.
Now you can finally start painting. Well, first I would recommend giving the white plastic of the inner part a good cleaning with a mild abrasive pad or similar to knock off any loose old paint. Be sure not to scratch up the clear plastic though, since you want that to look good.
It's OK not to do a perfect job on this, because really all you need is for it to be black without cracks. Beyond that is hidden from sight behind the lens. Here is a shot of a before (left) and after (right).
Also take this opportunity to give the smoked plastic lens some attention with a little soap and water. I found that mine had accumulated their fair share of dust over the years and a little work with a bristle brush to get into the nooks & crannies really helped restore their appearance.
Allow adequate time for everything to dry, and then reverse the process to put the pieces back together again and back into the door panel. Once you're all done, you should have a nicely finished assembly without that spiderweb of cracks that was so unsightly.
