3D graphics using c# and xna

Hi all,
I am working on a project that should get input from the user and produce
graphical simulation in 3D. For example, if the user enters the number of
planets, their initial position, velocity, size, etc the program should
create planets and make them move in the space. May be in elliptical orbit or
depending on their initial positions. Have to use physics for that. (not too
much detail needed about the appearance of the planets). There should not be
any user intervention once the simulation begins. It should just present
everything in 3D with decent accuracy, and should run consistently for a fair
amount of time. If the planets collide, it should be detected too.

I am pretty new to 3d programming, but I know some basics in C# and .Net. I
was told to use Java 3d programming for this project, but I personally prefer
C# .NET because of its user friendliness, and GUI.

I also thought of learning 3d max or blender, but do they have functionality
to get user input and run simulation according to the input ? are they easier
than C# ?

I would like my project to be numerically accurate and graphically decent
without much complications.

Could you please tell me whether it is a right choice to choose .NET and XNA
for my project ? What are the softwares required ? Any suggestions would be
greatly appreciated. I have to learn 3d programming first, so please also
suggest me some good books or tutorials that I could use for learning and
reference.

Thanks