Hi, once again!

I have lots of questions so you may be seeing a lot more of me in here. It's probably 15 years since I did anything like this so I'm a bit lost and need a little help and a few pointers. I'd like to install wifi/bluetooth and I'm not sure what I should buy? I mean are all the PCIe cards compatible? or am I looking for something specific? 

All help is much appreciated!! many thanks in advance!