Regarding the whole Andromeda collision thing...its unlikely to have any effect on our solar system (or many others for that matter).
99.99999% of the 2 galaxies are made of empty space...there will be very few interactions between the physical matter of the two. All that is going to happen is that the the two galaxies will start moving together rather than being 2 seperate galaxies.
The chance of anything in Andromeda interfering with the normal operation of our solar system is very small.