Is there a public source for B&W 600 series
tweeters? How difficult is it to change-out
or is it best to have an authorized dealer
(only source dealer) do the work?

In article , says...

Is there a public source for B&W 600 series
tweeters?

Not that I'm aware of...

How difficult is it to change-out
or is it best to have an authorized dealer
(only source dealer) do the work?

Personally I'd rather go to a dealer for the replacement, but I admit I
may be a bit overcautious in such things. fwiw, I do have 2 different
models from the 600 series and I do like them quite a bit.

--
Bill