I use DVD Studio Pro. The DVD doesn't have any subtitles on it at the moment. I assume that I'll need to remake the menu if I'm to add a subtitle button of any sort? If there is a way to keep the existing menu assets that would be great, but if not I guess the only way would be to take a screen grab and photoshop a remake of the menu background as best as I can and to remake the buttons? In terms of the DVD i figured that I'd need to locate each VOB file and what each is and to convert them all to MPEG2 and then add the new subtitle track. Am I on the right track? Thanks for the help!
Use the free program MPEG Streamclip - http://www.squared5.com/
it will convert the VOBs to MPEG2 files in one fell swoop and you don't lose any quality as long as you keep it at MPEG2. You can also rip the menu though since you are adding a button, you may still have to go into a program like Photoshop. Actually, you should be adding 2 buttons - one to turn the subtitles on and one to turn them off.