yeah Desktop PC's can be wireless. you just need to buy a wireless care and put it inside the computer :3 oh and the wireless card has to be compatible with your wireless box's frequency

Wireless as in have internet without a cable running around? Yes. But that can impact online gaming. You'd just need a wireless PCI card for your PC, those are cheap and easy to get.

Wireless as in be without cables whatsoever? No xD But I know that you meant the first thing~

Or do what I do and be too lazy to add the part you forgot to buy when you bought your computer and instead get something external like https://www.google.com/search?q=lin.....rz6UKrrGer-0gHv8IH4CA&ved=0CFwQsxg&biw=1920&bih=965

Yes they can be updated to wireless, you can either add an internal card (pci) or a wi-fi dongle which is the size of a pendrive and is very easy set-up.

yes. i think it's some sort of card or something you plug into your system (like installing more RAM). i've also seen that there are some things that look like USB drives and plug into USB ports. i'm not sure what these things are but i hear they are less effective than actually installing some hardware into the tower. some of these usb things seem to be real crap as a friend has gone through several companies until he found one that worked fine.

Yes, and it's not difficult.

Be warned, however, that no matter what anyone says you WILL get higher latency on your connection with wifi. It will probably only matter if you play online games, especially things like LoL where miliseconds can really make a difference.