Dark Conspiracy 1st edition uses the Twilight: 2000 2.0 rules (i.e. 1D10 skill check instead of the 1D20 check), the 2nd edition of Dark Conspiracy uses the rules compatible with the Twilight 2.2 rules. Besides updating the rules to make them compatible with Twilight 2.2 and Traveller TNE, the 2nd edition of Dark Conspiracy uses the same material as the 1st edition
Before you buy the pdfs as a bundle, have you considered buying the CD-ROMs from Far Future Enterprises? There's a lot of extra stuff on the CDs that somewhat alleviates the fact that 2nd edition basically just copied 1st (aside from updating the rules and adding some new adventures).
http://www.farfuture.net/cdroms.html