Yeah. I've been in an A320 simulator before for a few hours. They are pretty easy to fly and land. What isn't easy is getting one in a state ready to fly and to the runway. I can fly a Cessna 172 (didn't get enough solo hours for PPL though) and it's not difficult. Again prep is the hardest bit.
Oh yeah for larger jet aircraft certainly it is. I read that apparently the SR-71 preflight was so big it was performed by a backup crew and the primary crew had the option to simply jump in and fly if the timetable required it. But a small single engine aircraft isn't nearly as bad
Is the SR-71 the one that leaked fuel until it had warmed up and that required another jet engine to be attached to it to act as a starter motor?
It actually used a pair of V8 car engines as a starter
The latter is quite normal. There is an APU in most commercial jet aircraft.