To be able to take a current website's look and feel and convert it into a plone site takes a bit of work. It is a particular skill and requires the following abilities

1) An understanding of HTML, CSS and some idea of javascript. There are good tutorials on http://www.w3schools.com. Also, installing the Firefox tools to help webdevelopers saves a lot of time. http://plone.org/documentation/how-to/firefox-tools/?searchterm=firefox%20tools

2) A basic understanding of the plone system and using the Zope Managment interface (ZMI) This is covered by reading through chapter 1-4 of the Plone Book http://docs.neuroinf.de/PloneBook

3) An understanding of the zope templating language and the basics of creating a 'skin'. This is covered by ch 5-7 of the Plone Book.

4) The new way of developing skins in plone 2.5. There are two excellent tutorials that explain this very well:

http://plone.org/documentation/tutorial/creating-plone-themes

http://plone.org/documentation/tutorial/creating-custom-style

5) There are many sample skins to gain ideas or modify. http://plone.org/products/by-category/themes

6) That should be enough to get you started. If you want to have more specific help check out the documentation section of plone at http://plone.org/documentation and you can either look for help or type are search query for help. You can also chat with us on irc://freenode/cathnet. (To use IRC, install the chatzilla extension in firefox)