What do I need to process b&w raw files
You can use every program, when you first convert the .RAF files to .DNG (Adobe Digital Negative format). This last format is supported by older programs, too. So, don't pay too much. There are many programs for free, on the internet.
By the way, you can also use the in-camera processor, which is really great. I'm using the X100 for a year now. The greatest thing with this camera? I don't loose too much time which post-processing, because JPEGs out-of-camera are just great and usually I just use these JPEGs for simple adjustments, like frames, etc.
PS Adobe DNG converter can be downloader for free on the adobe.com