Whether you can do it in a month or not is hard to say, it depends on a lot of factors.
Is this a month working full time? Or part time? Or a few hours a week?
Are you writing it from scratch or using existing software.
Are you doing all the artwork yourself? Do you have much digital art experience?
For the type of game it looks like you want to make you will spend most of the time on artwork I think. For the software side I would recommend you take a look at the Unity engine and have a look at Fungus (http://fungusgames.com) on the asset store. It's free and makes it very easy to make an interactive story type game.
For the games I've worked on we have never used python in the actual game (for scripting we used Lua mostly) but I've had quite a bit of experience using it for tools and writing scripts to automate specific jobs.
It's a super awesome language and very handy to know.
I'm pretty sure the perforce merge tool is free to download on its own - P4merge. I have never had any problems with this and for c# files should be more than adequate. That's what I would go for if you want a free solution.
Yep Haps is right. Unless they've changed their procedure since last summer when I was messing around with it you need an internet connection, an xbox live gold account and something else which I presume is the AppHub membership that Haps said. I know I got a years worth of membership free from Dreamspark because I was a student if that helps but you still need the other things.
I would highly recommend GLFW, I just started using it recently having used GLUT all the time before and I really like it. It leaves your code clean and leaves you in control.
I only used GLUT before because that is what I was taught but now I realise it is outdated and a bit rubbish.