In my opinion the difference between GUERRILLA and INSURGENCY is very easy, when you just look at the words and their meaning:
GUERRILLA (in Spanish) means literally SMALL WAR, so it is purely military business and describes the hit-and-run tactics of small groups of fighters in comparison to the traditional warfare, where you have big armies confronting each other on an open battlefield.
INSURGENCY simply means that somebody tries to topple a ruling authority/government by any means possible. There is no limitation to the military fight (which is just a part of the whole insurgency). Special forms of insurgency would be a revolution or a coup.

The military today (a few at least) accept counter-insurgency being more than just military business, however the military gets all the money and still runs the show (Iraq: MNF-I; Afghanistan: ISAF) while continuing to neglect the more important parts (economic, social and political parts of counterinsurgency) of counter-insurgency. That's simply because military generals usually don't want to share authority and/or command.

BTW I found the Title of the older interim Field Manual "Counterinsurgency Operations" more appropriate than the new FM3-24 "Counterinsurgency" because the title suggests that the military part is the whole business.

BRUZ