there is a small screw that you need to undo before the unit will slide off its track, MAKE SURE THAT YOU DON"T UNDO THE WRONG ONE WHICH IS FOR THE FLUID PUMP AS THIS WILL CAUSE THE FLUID TO POOR OUT OF THE PUMP COMPARTMENT AND ONTO YOUR CARPET!! the screw for the pump motor is right next to the one to free the reservoir, i think the right screw to undo is the most forward one towards the front of the van..!
good luck, i have learn this the hard way!!

before you slide the reservoir back on, make sure that you don't pinch the tube for the fluid to make it out to the nozzles, as this would cause the pump to overwork and burn out on top of not having any fluid coming out! hope that i wasn't to confusing here, and that it helps!cheers. :D