As a developer I can hand on heart describe creating anything be it intranet/website in Sharepoint as a unique experience which is more akin to configuration management than development. Before answering your question directly I would offer these points as guidance which hopefully may save you time.
Ask the question do you need to create site templates/site definitions or are you going to build everything through the GUI. (My profile has multiple questions and answers about creating site definitions which I was unable to find answers for on the intranet.
Identify what Sharepoint can do out of the box or what exists on codeplex already, the number of times I have gone to code something and found that the functionality already exists or has been created by someone else.
Keep a very open mind, I have found that at time Sharepoint can be infuriating and at others very intuitive usually there are work around's.
Download CKS DEV from codeplex if you haven't already. http://cksdev.codeplex.com/
In direct answer to your questions
You can PROVISION a site from within VS2010, its not as simple as creating a load of aspx/c#/css/html and saying work on Sharepoint, You need to build things within the framework of Sharepoint. If its a website you are looking to build i would pay specific attention to the publishing feature. To build a site from within VS2010 you essentially end up creating a sharepoint project containing lots and lots of XML with a couple of templates and place webparts onto the templates using XML.
To change the look and feel of sharepoint you need to "brand" sharepoint usually meaning creating a new master page we used this as our base branding page http://sp2010.codeplex.com/. Removing the ribbon from use is a monumental task and not generally recommended. What you can do though is "hide" the ribbon from general users and show the ribbon to content editors/creators
I dont think this is a Sharepoint issue, I guess you could set a Sharepoint site up to be both a Intranet and Internet site the question is why would you want to do this? and not just have two instances of sharepoint one for intranet and one for website.
ULS Viewer for looking for useful sharepoint error messages http://archive.msdn.microsoft.com/ULSViewer
Some useful links that have helped me
http://www.codeplex.com Search here before coding anything
http://stefan-stanev-sharepoint-blog.blogspot.co.uk/ Blog looks rubbish but well worth visiting and reading for sharepoint issues
http://blogs.msdn.com/b/brianwilson/archive/2008/07/13/site-definitions-versus-site-templates-and-deciding-on-the-correct-customization-approach.aspx difference between site templates and site definitions
Hope this helps and have fun with begining your Sharepoint adventure