Modify a joomla template to a responsive design one, including third party components

General information for the website: Recipes website in Greece
Description of requirements/features: We have a template for a live Joomla website.. It is based on Joomla! 2.5. It has several known third party components (JoomGallery, jComments, Community Builder, Kunena, UddeIM pms) and a custom component.
We want to keep the current template, but convert it to a responsive one.

On its full view, it consists of two columns. One (left) contains the main content, and one (on the right, of 300 pixels), contains several additional modules, either general, (like facebook, ads, newsletter button etc), or specific to the content that appears at that moment (for example “content relevant to this one”, or “the content belongs to the following collections”).

The task is:
a) to create the html of the joomla template, that on its full view will maintain the current appearance.

b) the css for the joomla template.
The css must include styles for all the classes currently used in the website. (As does the current one).

c) Suggestions to changes in the html of the custom component and module pages (if needed) so that the design changes when the website is viewed from a mobile device.

The developer will get access to the current template html and css, and will have to work closely with the site administrator and our php developer.
Extra notes: