if it were me, i'd just measure the old fan and get one the same size. if you really want to get the whole kit, it's a bit hit or miss whether or not the fan will be interchangeable. 60mm always used to be the standard size for a fan on oem heatsinks, with 80mm and above normally reserved for enthusiast gear. don't know if this has changed in the last few years, however.
well, if it doesn't fit, you could always just super-glue it on. ghetto, but it works. i used to stick oversized fans on cpus and graphics cards with this method and it seemed to do the job.