If you are having knowledge about PHP, then easily you can do these things in Yii, just need to follow some tutorials. Also for any kinds of help wiki, forum etc. available on Yii Framework site.
Stop thinking … Start your work . You automatically know how YII works … Follow YII Forum. Google. Youtube. If you have any prob then share your prob . YII forum Members definitely help you…
Also I suggest take a look at Agile Software Development and break your project to several iterations.
I believe Project Management is very important at the beginning.without a good plan you have to repeat everything you wrote.
if you have OOP vision that’s enough.take a look at php courses on w3 school and read Yii guides and API documents.if something is difficult to understand,leave it for future.start with easy ones.try to imagine how a class would be helpful in your project when you reading it.