If it is feasible to travel through China I'd probably visit Nanjing and Beijing, then travel by train to Manzholi where I'd enter Russia and travel by train to Krasnoyarsk.
Otherwise, I'd likely fly through Amsterdam and Moscow to Krasnoyarsk.
In Krasnoyarsk I'd probably meet some others going on the tour and fly with them to Norilsk
Between the two Koryo tours I'd like to fly to Chelyabinsk in Russia, then by train to Karagandy and Shymkent in Kazakhstan, then by bus to Tashkent and the beginning of a tour, possibly guided by a friend, to Khiva, Urgench, Buchara and Samarkand.
I'd like to tour on my own through Khiva, Urgench, Buchara and Samarkand before flying from Tashkent to Biskek, Kyrgyzstan to join the second Koryo tour.
I'll likely fly home from Dushanbe, the capital of Tajikistan.