Hey, Psykotik!

Speed: Try shadow-boxing with weighted gloves, great for increasing speed and power. Speed also comes from technique, so work on your punching fundamentals using leverage and body mechanics to improve your quickness.

Blocking: Comes from experience. Probably the best way to learn how to block is in sparring. Once fists are flying at you, you quickly learn where it's important to cover up :) On the other hand, you should also incorporate blocking and defensive movements/posturing into your shadow-boxing and possible even heavy-bag routines.

When you ask "where do i start training", do you mean physically where do you start (i.e. at what gym?) or do you mean at what step in the process?

Assuming the latter, start with boxing fundamentals. And this should answer the question about knees and elbows, too: Repetition and practice. Through sparring and training (solely with boxing, no kick-boxing) you will get back into the swing of competition and most likely fall out of the habit of using your elbows and knees.

 Hope that helps!!