I'm going to steal a tad of the BA's thunder too...
1 -- the easiest galaxy to see at all is the Milky Way, because we're inside it. It's visible to the naked eye on a dark night as a band of stars running from Sagittarius up across the sky to Canis Major on the other side, according to my northern hemisphere star wheel (the MW continues on past these constellations, but is below the horizon then).
The easiest galaxy to see other than ours is M31, the Andromeda Galaxy. It is approximately 2.7 million light years away (ballpark math -- 186,000 miles per second X 60 seconds X 60 minutes X 24 hours X 365 days x 2,700,000 = miles), and is the furthest object visible to the naked eye. It is visible to the naked eye on a dark nite from a dark site, and easily visible even in small binoculars (the ubiquitous 7x35's).

2 -- in a few odd billion years or so, if I have the figures correct, the Andromeda Galaxy and the Milky Way will "collide" and rearrange each other. At this stage, no one's sure if the end will be two new galaxies, or one. See below for additional on this.

3 -- a galaxy consists mostly of empty space, so there are few if any actual planetary/star collisions. Other than that, there are hundreds upon thousands of stars (and there's no doubt that some of those stars have their own planets), and large clouds of dust and gas. There is a lot of change in orbits due to gravitational interactions, but there's not expected to be anything(s) running into each other.

Hope this helps, and an in-advance 'sorry about that, chief' to the BA if i'm in error somewhere or a toe got stepped on.

__________________
"If a tree is cut down in the rainforest, and is used to make paper to print a book, and the book is really bad, and there's nobody that will read it, do you still hear a sucking sound?"
Charlie in Dayton, A.AsC.