If you have never programmed before, youre up for a steep climb. I use PICS for many years, from 8 bit to 16 bit dsPICS. I would suggest you purchase a demo board (PICDEM2 PLUS) and an ICD2 from Microchip, but if the cash is low, there is another way. I implement the modbus on the dsPIC30F6014A and the dsPIC33 range which gives 40MIPS. The modbus is advanced programming, you need to implement CRC (Cyclic redundancy Check).
Whacko