The PCI slot is VERY complicted to use, but the project seems pretty pointless?, you can buy ready made FM radio cards at very little cost - expect to spend something like 10 to 100 times the cost you could buy one for?.
Also, don't forget you will have to write all the software for it, including Windows drivers!.
A single person doing hardware and software could easily take 6 months to complete from scratch. You have to buy the PCI spec by the way also and it's a couple hundred USD. You also need to be skilled with high speed layout and signal integrity if you want a chance in hell of meeting the spec.
First, you need to figure out how to build a receiver. For starters, a TRF (tuned radio frequency) receiver will do. You will find some receivers when you do a search for them on the internet.
Once you done that, you need to understand all of the signals the PCI slot consists of and you need to know when to read to and write from them.
If you make it that far, you need to figure out how to prevent the computer from making interference to your receiver, and you need to make software for it as well, because bios in computers today do not support homebrew devices.
Or better yet, DON'T USE PCI. Start off with a serial port and doing simple data I/O through it.