If just the thought of changing the drive lever in your Heiniger clippers scares the pants off you, you need to watch this free video (extracted from a web seminar I ran). Honestly, it's not THAT difficult. I've got it down to about 15 minutes. If you "purchase" this freebie, you'll receive a Microsoft Word document with a link to the video in it, which ALSO has links for the part itself and the screwdriver I use to take my clippers apart.
Enjoy!