I did a trade for some ships with a guy and just found out that I am missing the referance cards (found most online) and also

the instruction manuals. Example I am missing the four page pamphlet for the Shadow Caster, but have the model, all the cards and the tokens.

It is the paper explaining some of the new rules and the extra mission I found out.

Is there a good source to find the missing information??

http://xwing-miniatures.wikia.com/wiki/Mission_18:_Grab_and_Smash

The X-Wing Miniatures wiki should have you covered, I think. There's the mission.