I was a PHP person when my company switched to Sitecore, although we had an ASP.net developer.
99% of what is done in Sitecore is achieved without any .net programming requirement. A website consists of data templates, which are defined in the Sitecore desktop environment (much like Windows, but in a browser). Data templates define the fields that each type of page has, the workflow it is in and other content-centric things. Renders are then attached to the template - these are xslt files which take the data provided by the data template and format it into (x)html.
I'd recommend getting enrolled on the Sitecore Developer Training - this is a one day course which will get you fully set up and ready to start building.
http://www.sitecore.net/en/Training.aspx
Sitecore v6 is easier to build with than v5. There's also SDN (sdn.sitecore.net) which has a large amount of documentation and examples.
Also, as Sitecore is only available through Sitecore Partners, you should have access to a knowledgeable Sitecore Professional.