What to use to edit output after the fact?

[lilypond_user]

I've been using Lilypond to do all the homework for my composition class.  Of 
course, I was happy with a lot of the output, so I deleted the source files.  
(Yeah, yeah, I know, never delete anything...)  Now I find that I want to 
change the file, so I thought I'd just edit the postscript output.  I have a 
copy of Illustrator to use, but when I open the files, I only see some of the 
details, mostly just staff lines and a few notes here and there...

I have the most recent version of Illustrator and I'm not getting any errors 
when I open the file, so I'm a bit confused.  Does Lilypond output "standard" 
postscript?  Is there a better program to edit the output files with?

Thanks...
Doug