Hammerfly, I just repaired mine today. The top like you said is VERY hard to remove. I wrapped the Vamo main body with an old leather shammey and put it in my shop vice. Then put a pair of Vice Grips onto the top, held the lower portion with my left hand and just kept wiggling and wiggling (not too violently) until finally it came loose. Then you need to unsolder the old wires and re-solder them onto the new top. Somewhat tedious, but very doable. The new top diameter was not as large as the old cap, so I secured it with one drop of Loctite Super Glue and it seems to be holding up fine. You could also use one wrap of plastic electrical tape, or maybe some plumbers tape to make the diameter of the new cap fit tighter.
Best of Luck
The Old Wabbit
Best of Luck
The Old Wabbit