ive done a bunch, they are actually easier to do in vans then the trucks...
the trucks arent to hateful, first off, take the belt off, you dont have to slide it off of any pulleys, the tensioner has a holder to the (standing at the front of the truck looking at the motor) left hand side right where it pivots that you push up, witch then in turn locks the tension witch makes your life hella easier. so then once you got that works out, since you dont have a lift, shimmy on under the picker truck and pop off the two lines, i dont rember the sizes of them, the one is like right on the pulley, but once its pulled off, pulling all the bolts out will be alot easier.
the bolts, if your slick enough you can just get with a ratchet with a wee bit of leverage, there is 4 of them, once there off, bam its off the truck
every new pump i have gotten doesnt come with a new pulley, so transfer pulleys, and reverse my crude how to on doing this pump. make sure you bolt the pump up before you put the lines on, the bottom line is right where the lower more forward bolt comes out at, so it can make your job a bit more hard.
what makes you think your pump has failed?