I am trying to implement a $N$-body simulation of the Solar system and I am stuck on the issue of the simulation timestep size. At first I would like to use a simple Euler stepping scheme. Knowing that the error is dependent on the size of the timestep, I am not sure what to use for the model.

Would using a timestep size of one day be enough to get valid results? And also I would need to input the timestep in the model using seconds (60\*60\*24), correct?

Finally, where can I find values for the initial conditions that I should input in the model (initial positions & velocities vectors).

Sorry if these questions are kinda basic but my physics is about 15 years rusty... :)