Since I just learned this, I'll share what I learned since it may answer some Q's you (and others reading this) haven't thought to ask.
- The glass is thick and the hole has a metal ring inside it. You're not likely to break anything unless you are really heavy handed with it. Don't be afraid to play with it to learn.
- The "suction cup" is just a cover for electrical insulation. Don't be afraid to bend it back like an inside out umbrella so you can see what you are doing.
- If it's in right, it can move around laterally but won't pull out perpendicular. Give it a little tug. If it's in there, it won't come off.
- The clip has two legs. They squeeze together and then spread out again to lock into the hole, not unlike a christmas tree ornament. I find it easiest to put one side in and then push the whole connector toward it. This squeezes the legs together and the trailing leg will drop into the hole. Release and it's locked in.
- After you do this once, you'll laugh at having been worried about it.
EDIT: If you ignore the stuff about removing and applying silicone, this is a pretty good set of pics.
http://www.curtpalme.com/HV_Lead_Removal.shtm