I did the grip panel modification to my 22/45 MKIII several years ago, my total cost was about $5 (4 grip screw bushings) as I already had some spare 1911 grips and screws in the parts box. I removed the upper, and used masking tape on the areas of the grip frame surrounding the molded grip panels to protect them from the grinder and file, then started with a Dremel, and finished with a file.
You don't NEED to disassemble fully, but unless you seal up every nook and crany in the frame, the debris from grinding/filing will find a way in and require disassembly to clean it out anyway. Start to finish I spent about 5 hours on mine, including modifying the grips (some used wrap around pachmyer's i had) to fit around the slide release.
The answer to 1984 is 1776