The dice are just normal D6s. The 3rd ed missions are the same as 1st ed ones, some with minor modifications I think. So if you get 3rd ed you are getting 1st ed + Deathwing anyway, with some very slight modifications.
1) Yes, but you get all the stuff sans background in 3rd ed, and the [URL="https://app.box.com/shared/1jfco59hjv"]Deathwing background[/URL] is out there if you [URL="http://spacehulk.barsoom.cc/mirrors/shc/"]know where to look[/URL]
2) Yes, but most of the Deathwing rules are included in 3rd ed verbatim already.
So if you have either 1st ed + Deathwing or 3rd ed by itself you have the same game for the most part, I think from memory the main difference is 3rd uses 2nd's flamer system. Or just be crazy like me and get all the editions anyway...