Just do a google search for SD card SPI interface. Most SD cards support it that would be your likley first go. It's not easy though because you have to deal with the file system on the SD card. The easyist way I can think to do this is to create a text file or whatever on the SD card using a computer, using a binary sector editor find out the offset that the data in the txt file starts and ends and hardcode those addresses into your micro controller code, then just keep track of what byte in the file you're currently on and when you get to the end go back to the original offset. It would act like a simple circular buffer.
I checked the datasheet for your PIC, it'll run on 2.0 volts which is good because SD cards require 3.3 volt logic and power, so if you run the whole jobbie at 3.3 volts you won't have to mess with any logic level shifting.