How to start using Askbot for development?

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Hi there, good folks. So I have done the following:

1. Cloned Askbot into my home directory and cloned it as codebase.
2. Created my_site directory in home directory and setup askbot for development.
3. Created PostGreSql database and everything is up and running.

I need to do the following:

1. Extend Askbot to suit my needs. Since it is a 3rd party software, I want to extend it/ add features by creating new apps.
2. Changing Templates/ Skin I know how to go about.
3. Views and Models not so much but I can subclass certain Views and Models and create custom urls in my_site and point them to new Models without modifying the code.. Am I thinking right here?

What next...?

1. Should I create virtualenv with both codebase and my_site directory in it?
2. How should I use Git? Should I commit both codebase and my_site or use Git sub-modules and add Askbot as a submodule to my_site? Like mentioned in SO here -> stackoverflow.com/questions/677393/tracking-3rd-party-code-with-git
3. Where is this famous "default" skin.? I want to redo the entire look and feel of Askbot..change the entire skin..There were 3 ways mentioned to do this. Which way should I proceed with?

I have looked everywhere for a solution but haven't found a detailed answer. I am stuck here. Kindly help