Note that the current unix upgrade instructions say that you should touch
all the files in the kit to update the file dates.  This is to cover
the exact situation you are describing, ie, where the existing files
have newer dates than the ones in the kit).

Then you can do 'make update' (which I believe actually does the same
thing as 'make install' but is more intuitive when you are upgrading)
and everything should work fine.

Nathan