Louie,
As regards (1), I do have to do it pretty much across the board. The Minolta Dimage was a lovely camera (of its time) but lens distortion is quite noticible and the vast majority of the images are architectural/industrial in nature which makes it even more obvious. The end results are destined for a national archive, so I'd like them to be as technically accurate as possible. I'm only planning on doing this exercise after I've done all the "great nondestructive stuff", and immediately before a final review of vertical and horizontals - which is one of the two reasons why I need them back into Lightroom collections after photoshopping. The other being Mr. Friedl's Collection Publisher to generate the final output.
As for (2), it is true that "Edit in Photoshop" returns to the original collection, but Adobe didn't see fit to extend that facility to the "Export" command - even though they do provide an option to import the exported result to the current catalogue!
-Andrew