Most late model four wheel drive trucks can be lowered without a lot of work. If it is a newer truck with struts in the front then you can install a set of adjustable height struts to get anywhere from 1 to 3 inches of drop in the front. Belltech makes them for most applications.
If it uses torsion bars in the front then there are a number of torsion bar keys that are indexed differently which allow it to be lowered. On these same trucks you can also lower the front just a bit by backing off the torsion bar adjuster key bolts. But if the truck uses front leaf springs then we're not going to be able to help you out. You could always pull the leafs out and have them de-arched which will provide some lowering.
In the back nearly every four wheel drive truck is the same as the two wheel drive version so lowering the back is easy.
It would be negligant of me not to mention the lowering limits of four wheel drive trucks. As you lower the front of a four wheel drive truck with independant front suspension the drive axles "flatten out" You might not think this is a big deal but the constant velocity joints in the axles are designed to go through a wide range of movement as they turn which spreads the grease out and keeps them lubricated. When you flatten them out they don't have as much angle and they may wear out a lot quicker. If you keep the front lowering amount to about two inches this generally isn't a problem but if you go more than that expect to have to replace drive axles more often than you would on a factory height truck.