I have this one:
http://www.newegg.com/Product/Product.aspx?Item=N82E16833320173 Now this one is a little out side of a $800 budget but a PCI/PCI-E Wireless card is what you want.
If you can install a GPU then you can install it. It's as simple as putting it in the slot and installing drivers.
For Wireless cards it'd recommend NOT to skimp on them, buy the best one you can afford. It makes a HUGE difference. Definitely do not ever buy a wireless usb adapter if you want to play any type of competitive multiplayer game play.
Minecraft can be very cpu heavy at times, because java. If you arent running a lot of shaders and/or mods then a lower end CPU would probably be fine.
I'd recommend an i5 at the very least.
For CS:GO you really dont want a wireless usb adapter. The lag would be bad.
Samurai has a good rig here but I would switch out that Seagate Barracuda for a WD Black drive.
http://www.newegg.com/Product/Product.aspx?Item=N82E16822236625&cm_re=WD_black_1tb-_-22-236-625-_-Product Personally I dont trust Seagate Barracuda drives as they are the only drives that I've ever had fail on me. (Also from what I've heard from other people, Seagate higher capacity drives over 2TB can be rather unreliable, just something to keep in mind if you want higher storage.) I currently exclusively run all WD hard drives and Samsung SSDs.
If you can live with 2gb of Vram (which is enough for CS:GO and MC imo) then this is a solid build. I'd just recommend switching the WD blue to a black and maybe if you want to throw in a small capacity SSD for the OS (it pays off in the long run) do that. The wireless card you have is a good one. I used to have it in one of my older rigs, only issue I had with it was that it couldnt penetrate the thick walls in my new house that are between me and my router.
I'd say pull the trigger, this looks nice. Just post pics after you build it to show it off