this is gonna sound incredibly lazy... and it is... but does anyone know a good program for adding in some premade drum fills of the style that are in modern rap music? so I'd do my own main drum beat, and then just have those ridiciulous hi hat and snare build ups and fills and variations (THE SPRINKLER! for example) coming out of some presets patterns?

I don't know if there's anything in this package that will work for you, but there are number to download free to check the basic quality (some have MP3 demos, too). This guy does quality work.
 
http://www.prosonic-studi...-beats/rap-and-hip-hop

splice has sample kits with fills for modern rap production splice.com