This question cannot be answered without knowing more about your mechanical experience and knowing if you have the necessary tools and work space?
We can walk you through an engine change, it's straight forward if you are installing the same type engine, but it involves a couple of days work (I've swapped engines in one day, but it's better to take it slow and be methodical) and another person should be available to assist when you actually lift the engine from the truck.
Tip: It's not wise to change engines without replacing all coolant hoses and flushing the radiator and trans cooler.
Why did the old engine seize??