Ready for 4.3.. question about PHP upgrade first

[stevemills]

My host (Lunarpages) has finally installed PHP 5. I want to upgrade my store from 4.1.1 to 4.3 now, but I have a couple of questions.

Is 5 good enough, or do I need 5.1?

My store has quite a bit of customization (skin, other CSS, and more). Can I upgrade only the files necessary, without affecting these things?

Do I even need to do this?

This warning is added to my CP, before I even turn it on.

Warning: If you have any custom .htaccess content, it will no longer work and you will have to re-add the content. The content will be backed up to a timestamped .htaccess file if you required any content from it.

If you use FrontPage extensions, they will cease to function as they add content to your .htaccess file which will be renamed.

I don't edit my store with Front Page, nor do I use the extensions.

You may view my store here: www.pencilartist.com/cubecart/index.php, but be aware is is NOT a work friendly site. There is artistic nudity.