Search the forum! There are two or three really good posts on preparing for exams.
As for mastering PR, just do it. It will come when it is time. However, it will not come if you don't use it.
Don't pressure yourself, just relax and see how your skill presents itself.
I am familiar with your transition. It is easy and you can do it. The Data structure and Algorithm courses will be easy. The Discrete math is great.
I would suggest doing the Discrete Math and Data Structure courses before the Algorithm course. The Stats and Prob. are tag-a-long courses.
Have fun. Really have fun. 
Iam2 
