IL-2 is the perfect game because you can focus on flying and shooting while maintenance of avionics is low. This is in contrast to modern jet sims like Lock On.
Learning it will be an ongoing process, I'm still learning after a few years but as long as you read the manual instead of just trying to guess, you can be on your own within a few days, maybe a couple of weeks. IL-2 features an autopilot which can take over at any point in flight, including landing. This is not realistic for WW2 aircraft, but helpful for learning and cruising when you just want to look around. However, a properly trimmed airplane, in IL-2 or real life, will fly straight and level almost like on autopilot!
For dogfhighting make sure you understand how the padlock function works, this allows your "virtual eyes" to follow the enemy around the sky automatically. If you view is focued only on what's directly ahead of you you'll never track the enemy except for a fraction of a second when he's at your 12. Proper padlocking will also require a hat switch on your stick to "turn your head" around.
The best joystick solution for IL-2 is a Microsoft Force Feedback 2 with handle twist for rudder control. You can also use a comparable Logitech model. I stongly recommend a force feedback stick because the vibrations are very realistic and help you understand what the airplane is doing even with your eyes closed. There are phenomenal joystick-throttle combos out there but they're expensive and not really useful except for extremely complex jet sims like Falcon 4 and they don't have FF.
I have been flying IL-2 since its original release over 2 years ago and it's still on my hard drive. I also fly sailplanes in real life and those IL-2 aircraft behave just like the real thing. Phenomenal flight modeling, but the chief programmer is an experienced aeronautical engineer; if he won't know what the hell he's doing nobody will.