Are you commited to PIC design? If you are open to different solutions with less leg work and need a system that runs dedicated programs and do not require graphical operator input etc, then one easy way is to look at something like this.
The programming is very easy and if the programs are not that large they could all reside in the controller, initial programing is with the free downloadable software and is done with a PC through the serial port.
All the interpolation is done for you and it offers both stepper or servo output.
Just an alternative suggestion.