U should not go for the exam with panic. Plz read every page from K&B book. That book is great for the preparation. Don't go for the exam without completing that book. Take your own time.
If time is a problem for u, there is an option for changing the proposed exam date.
The mock exams given at the K&B book is enough for u. U don't have to try any other mock exams (if u read every page from K&B book).
I finished the SCJP 1.4 exam last month and got 86% marks.
I just studied the K&B book (nothing else) for 1 month and succeeded with ease.
If u have any doubt, mail me at : firstname.lastname@example.org