Check out Ed Sparks' iSpurGear model on
http://firstcadlibrary.com/ . You can find it at the bottom right side of the 'Gears' page.
iParts contain model data for a number of different variations of a single part and allow you to generate what you need based on that data. If you were to create an iPart yourself with the data you have on hand, you'd probably end up with something that's quite like Ed Sparks' model.
Otherwise, to my knowledge, there is no 'wizard' or similar in Inventor that prompts you for the gear dimensions and generates a model from them.