Hi soniya,
First of all, if you haven't already bought the parts, use the LM76, it has much better temperature resolution.
The interface to the LM75 is quite easily done through an I2C protocol, which is helpful because you don't need to do any A/D conversions, it is already done for you.
How familar are you with the PIC microcontroller? If you are just beginning, I suggest you go ahead and learn the assembly language. I believe the PIC16F84 doesn't have any hardware I2C peripherals, so you need to implement it into software.
The process of doing this is called 'bit-banging', which requires a bit of knowledge of how to control the I/O of the control and timing routines. Try to find some information on I2C, it is all over the internet. You need to generate start and stop conditions.. You need to pullup the outputs with resistors to Vcc. I recommend the book 'Serial PIC'n' by Square 1 electronics, which details how to implement serial protocols with the PIC.
Myself and most others agree that it is best for students to learn and do for themselves with the guidance of more experienced people. Initially, as I said, you need to learn the assembly or even learn a higher level language and use a compiler.
Steve