Ok, I've used this tutorial to convert the PAL movie into NTSC... but now I have a problem with the original DVD's menus and subtitles.

How would I go about (and is there a way of doing that at all) exporting those menus/subs from the original DVD and importing them into the new NTSC DVD?

Or... replacing the original movie (PAL) with the newly converted one (NTSC) while keeping the menus?

I really have no idea how to go about this... and creating menus from scratch is not an option (unless there's an easy way to save all the menus as screenshots and export all the chapter points from the original and import them into the new one so they look/work pretty much the same).