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. 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.
Please FAST FORWARDS to 9 minutes in, which is where the video starts ;-)