Joomla should be fine given your requirements and knowledge.
Out of the box it requires little-to-no knowledge of php - just a lot of patience in finding your way around it. It takes a few weeks to understand how it works properly, so as long as you've got time to understand how to use it properly, you'll be fine.
1) Not done similar myself, but there's loads of Joomla Directory extensions available - these are basically things that you install into Joomla via the admin interface to give you extra functionality.
2) As above, Joomla will be fine if you've got no knowledge of PHP. There should be enough out-of-the-box stuff for you to avoid touching the code.
3) Yes. You just need PHP & MySQL.
4) Have a look around the Joomla extensions site for payment stuff. There's all sorts you can do, including PayPal, Google Checkout, and Worldpay.
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