I found this guide to be pretty helpful:
I don't use schedules direct but rather mc2xml. There's a guide on the mc2xml page which shows how to integrate it with NextPVR pretty seamlessly (auto update and all).
In terms of black screen, I had a similar problem. You need to play around with the video/audio codecs. I have the Shark007 codec pack installed and use the LAV codecs just to get it to work. If you want to used XBMC I don't think you need video working in the NextPVR program as XBMC has it's own codecs which seem to work well.
Just keep playing around with it and you can get it to work. I've founds WMC "just works" while XBMC/NextPVR requires a little bit more tweaking/patience. The tweaker in me loves XBMC for that reason, but at times it can be frustrating.
Oh, and also the NextPVR wiki is pretty helpful: http://www.gbpvr.com/nwiki/pmwiki.php?n=QuickStart.QuickStart