Don't worry, these are different questions.
*breathe*
Volrath's Shapeshifter: I am playing against an Elf deck, and I smack him down to 124 life due to two Shapeshiftered Phyrexian Dreadnaughts. Trample Damage goes on the stack. Can I then pitch my Phage to make that damage pwn my opponent? (I understand that both my Shapeshifters die immediately to the new Legend Rule, but...Did Phage get her kill or not?)
As you say, they immediatly die due to the legend rule; At the time damages resolve, what does damage is not Phage, no reason for it's ability to trigger, your opponent will not die

Shapeshifter #2: I have a Trinket Mage in my graveyard (he chumped for the cause) and I cast Shapeshifter. Do I get to look for my cheap artifact via the CIP trigger of the Trinket Mage? (love those guys!)
You do so: shifter CIP, you check all the CIP trigger: there is one (the one of the trinket mage/shifter), so it triggers.
Shared Fate: Two are in play. Do both trigger when someone would draw a card? (Ie, remove the top card of opponent's library from the game) or does only one trigger (as you generally only draw one card at a time?)
There is no trigger with shared fate, this is a replacement effect. When someone draw a card, he decides which replacement effect will affect his draw. And because there is no draw more, the second replacement effet will do nothing

Same Question, but with a few of the various "Words Of ..." enchantments instead.
Thanks in advance!
Same as before: the one who is drawing decides which replacement effet affects his/her draw.