I think the main question would be do you currently have access to any resources that you plan on using to create this software? Do they have any experience in this field, or is this going to be a learning experience for them, just like it would be for you.
Estimation is very hard, my suggestion would be to try and find what is the minimum viable product that you want to produce, because in all likelihood you aren't going to be able to duplicate every feature that Autodesk has, and find some developers who have worked on this type of work to give you some idea of time. Even then figure that their estimates are going to be off and add some buffer. But still somewhat of a crap shoot because stuff always pops up.
Estimation is very hard, my suggestion would be to try and find what is the minimum viable product that you want to produce, because in all likelihood you aren't going to be able to duplicate every feature that Autodesk has, and find some developers who have worked on this type of work to give you some idea of time. Even then figure that their estimates are going to be off and add some buffer. But still somewhat of a crap shoot because stuff always pops up.
Derek