Having operated and maintained Russian SAM systems, I can guarantee that if you just want to shot down an aircraft at high altitude with any of their high end systems without worrying about what you are shooting at in a non ECM environment they are very easy pieces of equipment to operate. The Buk is not a new piece of kit (its been kicking around for 30 years) and was widely used by the Soviet Union before 1991 and in Russia and Ukraine afterwards. The system were designed to be operated by conscripted / reservist crews and thus are fitted with a high level of automation (to shot anything down with one of these systems all you have to do is get the system's tracking radar 'on target' and press the fire button as soon as a 'Target in engagement zone' indication comes up and the system will do everything else. While the equipment was also designed for rapid replacement of defective equipment which is very modular in nature and like most Russian equipment is built like a brick sh!thouse. Due to the fact that it was operated by conscripts for best part of 30 years, there will be a sizable pool of people in eastern Ukraine (rebels) who will be able to operate it and most likely a number of ex warrant officers or extended servicemen who where the personnel would normally fixed the things who would be able to maintain it. The main question I would ask is where did the missile system come from! Was it taken across the Russian border by the Russians (or from the Crimea) or was it captured by the rebels from Ukraine stocks in the disputed region. There is footage on the internet of the shootdown, the footage looks genuine and shows the aircraft just after missile impact, there is the smoke cloud from the warhead detonation and the aircraft which looks like a 777 is descending with the inboard section of the starboard wing from the fuselage to the engine and starboard engine on fire.