Yes, if you don't the cap will be ruined. You need a spanner pin to remove the back thread that holds the cap in place.
I recommend that after you remove the retainer you place your finger on the backplate connection pin to hold the cap in place, while you carefully set the pin on a sold and firm surface. Then slowly lift the cap machined body off. The actual cap will should be balancing on the pin.
Make sure it is a clean and stable surface so the the cap element does not fall over. If it does you will have to re-esemble the cap. Which isn't difficult but can cause dust and other particle to get into it, thus funking up things. If that happens, which you can tell by viewing impression in the diaphram when you re-esemble it, you'll have to use a de-static brush to remove them and re-esemble. There are also two thin mylar spacers that seperate the diaphram from the cap element and can be a bit troublesome but must be used and account for. So, just be careful and don't knock the cap over!!!!!!
Truth be told, once you've done this a few times it is no big deal but keeping things together and away from dust can save you some frustration.
Carefully punch the screens out of the body using your finger. The retaining ring will pop out along with the screens. Place them to the side. You will be using one screen after you have finished with the body.
Then take the cap body out to your shop and go to work on it.
Here how I machine it down.
1) Take a screw driver and place the body on it with the flange side pointing up.
2) Use a metal sanding belt type dremmel attachment.
3) Begin sanding the body, while it is sitting on the screw driver. (when you do so, you will notice that the body spins as it is being sanded. This is what you want it to do because it will uniformly sand the body down)
4) After you get down to a down to 1-1.5 mil stop. You can now round off the edges using the same technique.
5) Finish the job using scotch bright to remove any roughness.
6) Clean with 90% alcohol to remove any particles. Make sure it is totally dry before re-esembling. Any alcohol left in the body will ruin the diaphram.
Re-esemble the cap.
1) Take one layer of screen and place it over the cap, making sure it is in alignment.
2) Slowly slide the the body back over the cap.
3) Carefully lift one side of the body up and slide a thin stiff object under the cap pin. If you have small finger they will work if not use a thin stiff putty knife.
4) Apply enough pressure so you can flip the cap over and the pin side is facing up.
5) Screw the retaining ring back on. Make sure it is firm but not overtightened. You can feel the tolerence by removing the play in the cap. Just wiggle the back pin until there is no play.
6) Look at the diaphram in the light to ensure there are no impressions. If there is, most likely dust got between the diaphram and the element and you'll have to take the cap apart and remove it. (One speck of dust can cause problems, however, if you were able to keep the cap together after disesembling it you will most likely avoid any problems here.
For the side vents on the mic body, simply score the fins with a dremmel cutter. You do not have to cut them off. Then take a flat head screw driver and place pressure by prying on them. The fin should easily snap. Take some needle nose pliers and remove the rest off the fin.
You can use a file to clean up the remaining fin.
I hope this doesn't seem too complicated because once you do it, it is fairly easy.
I can do a two mic bodies and two cap bodies in about an hour's time. Your first time it may take longer.