Heya Elkinallen,
I have been modifying different aircraft in MS Flight Simulators for a long, long, time and (I'm not trying to rain on your parade) the hardest thing to do is to re-assign *.wav files for aircraft sounds. You could modify your 727 Sound.cfg file to add these additional sounds but it would be a lot of work.
I have a 727-200 for my FS 2004 and with it I use a Sound package from Eric Cantu called fx7222k2.zip.
An excellent package which includes all default sounds plus startup and shutdown.
You can pick it up here:
http://www.flightsim.com/cgi/kdl/main/53/fx7222k2.zip?ECQ4q002Just click "I Accept -- Start Download"
I hope that this helps.