I just rebuilt mine last night. It was not very hard at all. The plastic nipples for the vacuum lines were all broken off and the slides were stuck solid. Took it out of the car and did the following:
Removed the plastic switch from the metal bracket.
Cut the plastic rivet heads off with a razor blade. Thankfully didn't cut my fingers.
I pulled the slides apart and labeled each one. Cleaned them each with 90% isopropyl alcohol, let them dry and then coated both sides of all three pieces with silicone paste.
I then drilled 3/32" holes where the rivets used to be and tapped them for 4-40 screws about a half inch deep.
Now for the top.
I cut the broken vacuum nipples flush with the case. Then filed the area down to be smooth.
Starting with a 1/16" bit, then increasing gradually up to 1/8", I drilled out each nipple hole. I clamped my bits into my bench vise...I didn't trust myself with a drill to be this precise!
I filed the top edge a bit with a round file, just to slightly flair it. This will make pressing the tubes in easier.
I made sure to clean up and plastic shreds from around the holes. This is critical on the inside of the switch, where the little slider slides under the nipples.
I then cut (7) 3/8" ling pieces of 1/8" OD brass tubing. The tube has a wall thickness of .014", so the inner diameter is still plenty big.
I lined up each piece of tube with it's respective hole. I dabbed red loc-tite on each tube, placed the assembly in my bench vise, and slowly pressed the tubes into the plastic. I stopped every so often to let them rest to avoid cracking the plastic. I pressed the tubes down till the bottoms of the tubes were flush with the bottom of the plastic, so the slider wouldn't bind on them.
I wiped up the excess loc-tite and blew out the tubes. I the super glued them all at their bases in the top side of the plastic.
I cleaned the slider and greased it, then reassembled the upper half of the unit.
For extra measures (okay, okay because I'm a bit OCD), I filed the tops of the tubes so they were all flush with each other as well.
Finally, I screwed it together and installed it in my car. No more vacuum leaks and bullet proof for years to come!