Glue a small eeprom onto thr loadcell and store the calibrationh data there. That way you can replace the lodcell on service calls without recalibration.
Your project is very doable, what is going to give you the most headaches is digital noise in the analog circuitry. DO NOT skipm on using a 4 layer board with analog and digital ground separated but for one point, it will kill you if you don't.

Erik