>Is the D300/24mm f/2.8 AIS Nikkor a good compromise >combination (e.g., the 24mm f/1.4 is way beyond my pay grade), >given that I'd have to manually focus?
That is a decision that only you can make. Were you happy with the 24mm on your D200? If you can take your time, MF should not be a problem.
>Does the D300 have the >"green spot" manual focusing aid like the D700?
All in all the D300 can be easily used together with the D700 without thinking too much about it. Their control layout and feel are so close it can be easy to forget which camera you have in your hands.