Hi Mikey - I think you asked how long it takes to get up to speed in responsive. You are a programmer, so HTML should be a weekend. Responsive CSS is the core that you need. Responsive is like playing the guitar. You can be “sorta good” in a month. To be a virtuoso takes longer. Here are some more links:
Prebuilt PHP/MySql CMS solution. Free to learn. $40 license per site you add it to with 3 months included tech support from them I’ve learned it and tested it. Haven’t installed it on a client site yet.: http://www.couchcms.com
Here is the seminal article on RWD: http://alistapart.com/article/responsive-web-design