There are several ways to do this. The easiest is to put your entire video on your timeline and:
1) Set the Work Area Bar (the light gray area along the top of the timeline) over the segment you output.
2) Go to Share and select the output destination or file type then, before you begin output, check the Work Area Only box.
Also, I'd cut the long sequence at specific parts (roughly 10 min as you said) so you don't cut in the middle of the action. Just use CTRL+K with the time marker where you want the cut.
That way you can easier set the Work Area as it will snap to the cuts you did. And finally, if you want fancier stuff you can put fade ins/outs at those cuts for a smoother viewing experience.