It can be a little tricky if it gets hung on the flywheel bolt. Once it is broke free I remember having to hold the crank side tight to the engine, pulling down on rear side (towards the front of the engine) and the tugging down on the rear (rear). Sounds kind of weird but it will make sense if you encounter it clearance problems.
On later models 4.9L engines depending on the model the exhaust may run over the pan. The Y pipe will have to be removed. It seems like on the 4.1L there was an air tube or something that had to be removed. Other then the two above it is a straight shoot besides the flywheel dust cover.
It is pretty easy to get the 4.9 pan off, can't speak for the others.
Taking it off the first time you have to be careful, I remove the oil pump with the pan, then you just grind down the two ears on the back of the pan and put the oil pump back on. Put it all back together and with that small amount ground off the pan it will slide right in.