I would highly suggest looking at google guidelines. http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml
They are aimed at taking some of the landlines out of c++ and give pros and cons for each argument. There are many places in the gcc source where we are already doing C++ things. I would think those would be the best places to start. Adding classes (especially with inheritance) should not be a development decision but instead a design decision. To really move towards C++ we really need to develop a model of what we would like the code to look like.