Confusion about driveshaft/transmission removal

[toddtheodd]

The books tell me to "undo the ubolts on the rear of the driveshaft and push towards the front of the car to disengage from rear end." Then to "pull back to disengage from transmission". I've looked at the ujoints on the front of the drive shaft and they are the kind that are always pictured being taken apart in a vise.
So my confusion is this. Can the yoke just be pulled right out of the transmission like that? Does it slide right back in just as easily? Wouldn't that cause the fluid to leak out?
I can take a motor apart and put it back together again, but I've never done this before and the books I have are confusing.
Todd