Mike,
Loadmaster is one of the best enlisted career fields in the Air Force/Air Guard. I would recommend it to anyone interested in serving their country and flying/travel.
I'll start by saying I am not a loadmaster, but as an airlift pilot I deal with them every day. Most are extremely motivated about their job and just as professional. As with any career, there are negatives (living in tents with others in some not so great locations where they do not allow booze, dragging about three times as much "luggage" as you would normally, practicing for chemical warfare, and box lunches to name a few). However, the good still far outweigh the bad, in my opinion. There is no other job I can think of where you could transport a critically ill infant to a location where medical treatment is one day, then haul the President's limousine or Secret Service detail the next week. You would have the opportunity to see places, most people only read about, if they even do that.
As a loadmaster you would be responsible for the proper loading and unloading of cargo, handling of passengers, interaction with medical crews, and possibly the airdrop of personnel and their equipment. The cargo could range from a small box hand carried on to the aircraft, to pallets of cargo weighing thousands of pounds. You would be responsible for ensuring whatever is on board the aircraft is properly restrained so it doesn't shift while the aircraft is in motion. The weight and center-of-gravity calculations of the aircraft are also computed by the loadmaster. You would also have to know what kind of hazardous material can be carried with other cargo and/or passengers, as well as the required paperwork to transfer the cargo and clear customs when appropriate. Loadmasters are trained to handle a variety of emergency situations, and are critical members of the crew in those situations. They are also trained to operate in a combat environment, using tactics and procedures to perform their wartime mission. (If you research it a little, you'll see the C-130 has been the workhorse for combat airlift for decades, and will probably remain so as long as it is in the inventory.)
The active duty C-130 schoolhouse is at Little Rock AFB, AR. I'm fairly certain the Guard sends their members there for training too. The training there would consist of academics and flying training with a flight evaluation for the qualifications you are to hold. You would also have to be trained on the physiological effects of flight (altitude chamber). After initial qualification, you will maintain your proficiency by accomplishing continuation training at your unit. Once you have enough experience and you're ready, you would be upgraded to Instructor Loadmaster responsible for training other loadmasters who are non-current, or need additional training. The next step would be Evaluator Loadmaster, administering evaluations to other loadmasters ensuring they are adequately trained to perform their duties.
Best of luck in your pursuits.
MOOSE