How many notes are there in the piano part of Rachmaninov's 2nd piano
concert, 1st movement?
How many (still just for piano) are there in the whole concerto?

Hi Ben, 

I have looked into this for you, and there are places where you can
pay for the full score etc and also places where you can get it for
free, ie the digital archives where Rahmaninoffs pieces are kept. 
There are 123 notes in the introduction alone for piano (10 bars) so
physically counting each individual note for the whole of the piano
section would take an extremely long time for any normal person.

Have fun finding the answer