Darth Lefty 

It's way easier and cheaper to trade in your bike for one that has discs to begin with. If your bike has the tabs for the disc caliper then it's certainly possible. But there are more parts involved than you hope. You need to replace the hubs. If you don't know how to build wheels then you will have to pay someone to do the swap and it would probably be cheaper just to replace the wheels. You need to have not just the calipers but the discs and adapters, and replace the cables with longer ones that go all the way to the hub. If you want hydraulic that's the levers too.