Radiator Flush and a/c removal

I am still having problems with my car and the cooling system. I have a leak somewhere (maybe the radiator) and I am thinking about replacing it this weekend. I want to flush the whole system as I do it because Im seeing a lot of white gunk in the radiator filler neck. What is the proper way to do it and what do I need? Anything that I should do when I have the radiator out? I replaced the thermistat already but Im thinking of getting a new nissan oem part, I hate aftermarket crap. Im also pulling my a/c (it has never worked) and need the shorter belt, anyone know the part number? Any suggestions on brands of belts?? thanx...