Taking a ProVari apart is extremely simple...
I use a very fat center punch / scribe... Push the scribe
through the battery opening and around the circuit board until it makes contact with the top cap... Pop the handle of the scribe on a hard surface to pop the top cap off... The wires going to the circuit board will keep the top cap from flying off... The circuit board is held in the tube with 2 dots of hot glue... Pull those off and the circuit board slides right out... The top cap and circuit board can be removed as a single assembly.
Make sure to catch the button when you slide out the circuit board... Remove the two screws holding the window in place. Press the window into the tube and catch it on either end of the tube.
Done!
Literally takes like 1 minute or less... Took longer to type how it's done
Putting it back together is the same in reverse... Just be careful not to pinch the O-rings on the top cap where it press fits into the tube!