You should be able to go into sounds...then alerts...and assign specific ringtones to texts, pics, video's, emails, voicemail, etc.
as for assigning ringtones to specific contacts...that's done through the contact area itself.
Same goes for incoming ringtones. Go into sounds, then assign a specific ringtone to all incoming calls.
REMEMBER: You can't assign mp3's or full length sounds as ringtones. They must be cut down parts of a song, and they need to be in your ringtone folder on the phone, and not on your memory card.