It takes about an hour to get it on there nicely. It's not complicated or difficult, and helps to have a friend, it's just that there isn't a lot of room to get your hands in there to position it correctly. You can see in the TM, you raise the cab, take out one bolt on the top and bottom of each side of the radiator (4 total), carefully fish the cover up from the bottom into the small gap between the radiator+intercooler and the bumper/hoses/etc., and reinstall the bolts.
The cover makes a big difference when it is really cold. (Actual "cold", like below freezing and below zero, not "I need to wear a sweatshirt today" Floridian-cold.) Otherwise, the engine may not even be able to ever warm up. If you're not working the truck hard (e.g. towing, heavily loaded), you can run the cover even while it's quite warm (e.g. 80°F outside) and the fan will still keep up, but the fan will be running a lot. I probably wouldn't bother running the cover unless you're going to have days in the 40's or lower, and nights below freezing, fairly consistently.