Hasta La Motion!

Hi everyone, I am pretty knew to all of this and I would like to ask some questions. I really want to get into this and I have bags of passion, and I am very willing to put the hard work in.

First of all can someone helpo me define what it is I want to do? My interest lies in added visual effects to existing footage. For instance, I might go out and film a guy in a field, with a prop gun, then I want to added in gun fire muzzle flashes, an overhead jet speeding by, also firing a missile, adding an explosion as it hits the ground, etc. Basically I want to (ideally) add photo-realistic visual effects to actual footage. Is there a name for this? I am NOT really interested in making full-on stuff like what Pixar do.

So now knowing what I want do, what is the best software(s) for me? I see stuff on the internet that has usually been created by more than just one software package.

I recently purchased After Effects, but I have heard of many others. Maya, Shake, 3DS Max, Nuke, etc,etc. Can anyone tell which one of which ones I should invest in. Would you recommend starting with a particular one first before any other? Are they all similar to use or vastly different?

Also can anyone tell me if my laptop is good enough. The thing is computers ALWAYS seem to get better and better every day. I kinda think which ever knew one I buy will be the wrong one again 3 months down the line. My current laptop is a Toshiba Satellite A300 21H and I don’t really have the money to buy another. Please google it and tell me if it is adeqaute.

Thanks so much for any info people could give me, thanks.