Normally, loosening the alternator/generator will provide enough slack in the belt to slip it off the bottom pulley first, then over the fan blades, one at a time, turning the fan by hand. Then slip it up over the top.
That is of course, unless you have a front mounted hydraulic pump. In that case, you'd need to remove the bolts holding the pump on the front of the tractor, pull the pump forward separating the drive shaft from the crankshaft pulley. The Ford/New Holland online parts catalog is down at the moment, or I would have provided a a link to an exploded view of that assembly. Not sure if that has a universal joint type shaft, or a splined one. Either one will need to be disconnected from the crankshaft pulley, so as to slip the belt off.
If you post in this question in the Ford New Holland section, hopefully RickB from North Caroline will pick up on it, and answer your question in a heartbeat. He's a pretty sharp cookie on the FNH tractors.
