i doubt that you'll have that long for the nuances of the differences.
most of the basic commands appear to be the same and 'man' is always your friend.
on the version we have here 'rsh' (solaris) is 'remsh' (hp-ux), tar has minorly different arguments, and administration is so wildly different i couldn't tell you which files to modify, but it is an old version of hp-ux
the networking is modified GUI style aka linux, using SAM (i believe thats what we use), and adding printers takes a good while to work with (being hp, they talk PCL easily, but not PS so well).
I'm not really an hp-ux person either, there are lots out there.
the only reason i have to play with it is that we have a mass-spec linked to one, and the tape drive is knackered on it, so we put it on our network and tar the files off for backup.