IMO as a housepainter, as long as you use aquarium specific silicone caulking, then once it fully cures your tank won't be harmed.
And with the leak being at the top of the tank, you're chances are good for a patch job. Or at least, if you had to have a leak, then that's your best place for it. small consolation i know.
When i was researching possible solutions for a leaking 180 glass tank, the collective opinion was to totally remove the leaking panel and then reseal the whole thing.
I hope the caulking works for you.
good luck,
po
[ April 13, 2002: Message edited by: pojohnny ]</p>