Hi I'm absolute beginner and I have couple of questions

I want to use PIC16f84,so I need to buy it and buy a programmer,right? I think there are more things to buy ...

What pre-knowledge do I need b4 starting programming? I know assembly,c++,some electronics...hmmm?

You will need the PIC, a programmer, breadboard, crystal +caps, MPLAB, and a lot of patience. What type of assembly do you know? PIC assembly is a fair amount different than X86. Take the time to read the datasheet of the PIC. It will familiarize you with the architecture, operations, and command set of the PIC. Also look for an MPLAB tutorial on the web. I know there are a bunch of them out there.

I come from the same family C, C++ and Java and one book that I would like to recommend is Easy PIC'n from Square 1 by David Benson. Also, down load MPlab and start practicing inmediately. Good luck!!!

Alright,great answers...Since I don't like building circuits that I have no idea how they are designed,i'm gonna buy a programmer,do you recommend any?

Is there a socket in the programmer so I can change PIC's?

In my opinion this is the best for the price.I have had zero problems and use it with a pretty wide range of PICs.Also it is well supported and cheap.

www.melabs.com/products/epic.htm