You can buy silk screens already assembled at art store. Then you need to apply your image and your ready to go. The blocked out image can be done several ways. Traditionally artists cut out their image then transfered that to the screen. Now they have photo sensitive ways of transfering images that gives you more detail then cutting can (and laser cut screens too). Most art stores sell books on the topic and can guide you through the process. If you go to a nicer art store the counter person could walk you through the process and set you up.
It's not hard to do but it's probably more then most people are comfortable doing.
If you really wanted to do this cheap, go to any local community college and talk to the professor in the art printing department. Students are always thrilled to make a buck actually practicing their craft. Some professors will do it for you too, but they'll charge professional prices.
There are sources to have this done commercially but I don't have their names near me.