Sorry Mr Fluff, missed this - should be in Q&A. Not really sure its worth getting it moved though, seeing as the questions are both fairly easily answered.
Anyway, on to your questions:
1. I don't believe Graia was destroyed at all. It is still listed as an active Forgeworld in Imperial Armour 1, Forgeworld produces at least one Graia pattern vehicle for 40K (a Hellhound), and I can't recall any background stating it was destroyed. I'd assume its still active and Loyal.
2. Yup. Again, Imperial Armour 1 states that Graia is still the homeworld for the Morning Stars Legio in the 41st millenium.
Have a look
here for further Titan Legion info. If you are going to go for the Morning Stars (Legio Astramana in High Gothic) I'd replace the yellow banding of the original scheme with gold - will look better in my opinion, and fits with the rules of heraldry anyway, where white/silver and yellow/gold are interchangeable.