I think it's very possible, saw a documentary on it on youtube, It might take some time, but the method they describe only works from when the time machine is set up, and thats the earliest point to which you can travel too...
I wouldn't try it, and I cant imagine the all the trouble it would cause....
And also very complicated :S Like the idea of going back in time and killing your ancestor, you wouldn't be born, so how could you kill him? But you just did so what happens to you? What if you go back in time like way back and kill lots of people using a gun, how can you use something that wasen't even known and then how many people would die?
The only normal way which you could travel back in time is probably to go into a black hole i think, which is pretty far
SO my final answer is, if I could go back in time, I wouldn't, I forget about my past if I dont want anything to do with it, but I think it's wrong to go back in time and change it, but I also think it's possible.