there is no differance from one box to another, they just have differant plug patterns. you can just swap the wires to a differant plug if your comfortable doing it.
As far as buying the program, if your not going to be racing id say save your money, the pre-programed curve are already going to be better then your stock box. If you worried about too much advance do a comp test and post what you got, based off that you could figure out if curve 3 (most advanced curve) would advance too much or not