The information you've provided doesn't seem too bad, though it may be worth checking now, whether you can actually get the motor spinning at 1,725rpm and producing 12V using your arrangement of gears etc.
The diode you use just needs to be rated for the voltage / current it'll operate at (I'd recommend at least a 25% margin of error though, to be on the safe side). Bear in mind the voltage drop of the diode also.
That's a pretty big battery, and it's 12V - unless you're confident you can generate well over 12V, it may be difficult to charge, especially with the voltage drop from the diode. Depending on how much current you can get from this source, 28AH may also be too high capacity to be worth using.
I don't know much about charge controllers so I can't help you there.
Why the inverter? What are you planning on powering from this supply? Is it going to be a substitute for a mains supply?