[Are purple mods available from vendors/quests, or just cybertech?]

the Green =[RE]=> Blue =[RE]=> Purple thing is applicable to every crafting crew skill. There may even be several different blues obtainable for a single green base item. That means a green can yeld several blues, which in turn will yeld a more powerful purple each.

So far (level 35 Sentinel) I've seen only twice purple mods in quests rewards. So I guess the best thing to do is either to be cybertech (or to have a friend who is), or to buy them on the GTN.

[need help finding component!!!]

If the component you are looking for is green quality, you can find it in gatherable nodes on adequate planets, or by running missions. Blue and purple components can only be obtained through missions.

[why does Guardian get the healing companion so late?]

C2-N2 (granted with every republic ship) can heal. Though he's not really a companion as he doesn't fight, he can heal. You'll just have to find him some equipment by your own.

[color crystals]

Am I the only one to find weird that orange crystals can be found only in custom DS restricted lightsabers, even if the crystal itself is'nt restricted to dark side ?

 

PS : I know orange crystal can be crafted at high artifice levels, but there is only one craftable for now.

[Epic Reagants? Where?]

I got a few epic gems by running treasure hunt missions. But they're really rare.

[Upgrading T7]

if you have moddable armor pieces, you can upgrade the mods, either by crafter better ones, or by buying them on the Market. All moddable droid pieces have no stats (besides armor) without mods (as with every custom lightsaber).

[Sand Demon too strong]

I tried it a few dozen times without luck (no matter if Kira or T7 was present) I then switched from ataru form (I specced in the combat tree) to juyo form. beat it at the first try.