Whiskey's mono on mono time it probabley your best choice for a complete and thurough walkthrough. In a nutshell though:
Unloading supplies in an M3 - From the driver's position ("1" key), open your cargobay ("O" key) and when at a complete stop within range of your objective simpley release like you would a bomb on a heavy (I forget the default keyboard key to fire secondary, but I do remember it isn't mapped to your controller/mouse by default for vehicles (although it can be, like I currenty have it on my own settup)). Same method for droping/delivering all supplies and troops in GVs.
Firing guns - if it has a gun position, try to occupy it with the "2" key (or "3", "4", etc.). Similar to bombers, you can steer with your rudder pedals while in the position, and returning to the driver's/commander's position is the "1" key. There is so much more, like adjusting your gun sight to compensate for range, but that should get you started until you hookup with Whiskey.
