Not hard, once the fan and shroud are off your can have the pump out in about 15-20 minutes. Belts pop right off, WP pulley is 4 bolts and you are there. 4 more bolts and the pump is off. Sometimes they are hard to pull out. I usually can have a M50-54 Water pump job out in about 2-2.5 hours if I have no interuptions. The 4.4 is a little harder, but there is nothing out of the ordinary with the job, it just takes a lot more time.

I have never needed anything special to do the job. The X5 is one of the tighter fits to get the fan clutch nut off, but it's doable with a regular 32mm wrench and screwdriver.