Yamaha DTXpress/DTXplorer/DTXtreme

I just ran across the dEXTD program, and since I recently got a
DTXpress II it sounds like something i'd like to use. I have a few
questions about it if anyone has used it before.  

1. What kind of cable do I need to connect the module to my PC? I'd
imagine a MIDI to MIDI would work, but I don't have that input on my
PC. Would a MIDI to USB work instead?

2. Am I able to add custom sounds or edit the preloaded sounds on my PC?

3. Any other important information before I try this?