Shawn Wright said:

1. Could this noise indicate imminent demise of my tranny? Would
draining it and checking for excessive metal on the drain plug be a
good idea? I hate to waste the Redline...

Then strain the oil with an old pair of your wife's panty hose (or your
own).  Simply pour from the drain pan into a clean container through the
hose.  Cheapys like me wouldn't waste generic gear oil with 25k on it, not
to mention high dollar stuff like RL.