[Theme: Twenty Eleven] – Newbie Questions about use.

hey!

I am new to WordPress and have some questions about theme Twenty Eleven.

1 – Can I alter it to fit my needs (cosmetically and through code)? Meaning – can I use it as a base template for future sites until I learn to create templates on my own?

2 – Once I alter it – what procedures should I follow to ensure that theme updates won’t overwrite what I have done?

3 – I would like to be able to continue to accept theme updates – if wordpress themes get updated – as I am sure they are beneficial to the theme. But would manipulation of the theme prohibit this?

Sorry if these are simple questions. Just starting out. Hope you understand.

Thanks!