can any1 give me the instructions how to install Hildon-desktop app manually.

Yes, sure.

Yes it's absolutely possible to lock on portrait mode, you can even set independent wallpaper for portrait . This is what i've done (I consider you're already have cssu installed). It's quite tricky, all you need is gconf-editor (get it from ham or fam). Open gconf-editor, once you in, you will see path structure at the left side of your screen. Then go to /apps/osso/hildon-desktop/ in the right side there is a lists of configuration related to hildon-desktop, you can define, off or on some features from this place. So since you are asking about the possibility of portrait lock, then scroll and find string "edit_mode_portrait" in the right side and tick the checkbox, next scroll and find "orientation_lock" and "orientation_lock_position", and tick the checkbox. For extra, if you want to set different wallpaper in portrait mode, then scroll to the end, and tick for "portrait_wallpaper" and "ui_can_rotate". After you've finished, exit gconf-editor then restart hildon-desktop by execute "killall hildon-desktop" from terminal. And you are done
To lock on portrait mode, you have to tilt your phone until the desktop turns into portrait then go to statusbar and activate the orientation lock. -cheers

Will the locked portrait mode persist across reboots? That was the hard part from the previous package.

Also, if I could just completely fool the hardware sensor to think it was always in portrait mode that would be fine too.

Edit: I was unable to lock portrait mode on my phone with CSSU installed using this method.

vask: It worked for me, but I noticed there was no "edit_mode_portrait" key as batarawatson said. Instead, I had to uncheck "orientation_lock_position" so that it would use the current orientation and not always switch to landscape.