Advice needed on approaching to Drupal 6 and jQuery Mobile I'm pretty new to this 'world of Drupal', and I've got this project, where I need to build a jQuery Mobile site based on an existing Drupal 6 site.

The mobile site is somewhat different in it's structure, but needs to get some data/content from the original site. 

What is the best approach to his project? Should I build the mobile site based on the same Drupal-installation, as the original site? Or should I build a new site using Drupal 7 and then somehow export/distribute content from the original site? 

I've read a couple of articles claiming it's quite difficult to upgrade jQuery to version 1.4.4 in Drupal 6, which is needed to run jQuery Mobile. Is that so?

My concern is, that I'm not a PHP Jedi Master (though I know some PHP), and therefore it would be great, if some could tell me, what the best approach is to this.

I found this articles yesterday: http://www.adyax.com/en/tutorials/make-mobile-version-your-drupal-site-using-jquery-mobile-and-some-magic/lets-get-started. Is this what I should be doing?
I personally don't recommend splitting the project in 2 sites but rather in 2 themes. If the project is slightly different (I assume you however use the same database) then try to customized it via theme (and theme functions).

I suggest you use the Omega/Fusion Theme which are responsive themes.
A responsive theme doesn't need a special redirection.

However if you need more customization in additional install Mobile Tools Module.

Then create a domain called m.domain.com in additional to your site domain.com and set inside the Mobile Tools Module based on a agent to switch to the theme needed.

There's indeed no need to install Drupal again.
You should ask your host to treat the m.domain.com as an alias for domain.com. That way it points to the same Drupal installation and the theme switch can take place.

If you don't have a mobile to test install Firefox addon: https://addons.mozilla.org/en-US/firefox/addon/user-agent-switcher/