If you know how to fly, it's not so bad. You can be walked through engine start-up procedures and basic targeting/weapons release in about an hour. Flying it efficiently in combat situation takes years of training. But if you simply need to know enough to take off, take a shot at a target, and come back to base, it's quite manageable. But like I said, you have to know how to fly to begin with.
I doubt a modern fighter aircraft court be flown at all by an untrained pilot. Have you seen the inside of the cockpit for even a single-seat Gen 4/4.5 fighter?
The pre-HUD, pre-voice-activation, multi-display stuff must be even worse.
Pre-HUD stuff is much easier, by the way. Sure, there are more toggles and switches, but they are all right in front of you and labeled. And you only need to know what a handful of them do to get a basic mission done. If you are flying glass, you have to know all the menus and options. It's a lot more work to learn.
I asked my friend if I would be able to simply take off and fly. Even if I crashed within minutes that would still count. He was pretty confident that I could. I just looked at a high-res picture of a cockpit and I had at least a general clue of what most things could be for. I found the keyhole and what I think is the start switch. I would be scared to death trying to take off in one though.
edit: I don't know how to fly, never even played on a flight simulator. I do understand the general physics of flight and the basic controls of a plane. Have you ever flown a plane?