I have a similar setup to yours. I do a lot of this type of thing, usually by myself. The gravel section is usually the real problem. Here's some of the solutions I've used. Maybe there's one or a combination that works for you. It'll get the creative juices flowing anyway:
Snow and anything that resembles a toboggan - probably not for NC.
Just drag the pallet with a vehicle.
Put pallet on two 4x4 lumber with ends cut to be runners, then screw pallet to these skis. Works great on snow, and much better than just a pallet on gravel. Push/pull/drag as appropriate.
Arrange for an off-road pallet jack (big pneumatic tires and a wide stance). Regular pallet jacks are about useless on gravel.
Carefully push pallet with a plow blade, UTV works best for this. Power angle blade can be a real help.
Any vehicle with a winch is handy to have around.
Extra hands and bodies are good to have around. Strangely, weaker is usually better. The tough guy types often contribute to injury or damage.
If you have a chain or better yet a stout strap, it's amazing what even one person can do in moving palletized items. You just need to be able to pull from a position where you can make some real power, and the chain or strap allows that.
A rock bar or crowbar will allow you to lever almost anything around in very small increments. Also makes a good turning / steering brake when dragging things.
Once on a paved surface, a lot depends on what you're moving and what you're willing to subject your surface to:
Furniture rollers can sometimes be amazing.
Vehicle floor jacks can also be lifesavers.
The old pipe-roll has already been mentioned.
In the push/pull/drag scenario, simply wetting the sliding area can be a real help. Creating a snow-packed sliding surface is good if it's available. Creating ice can be great, or too much of a good thing, depending...
Rock bars / crowbars work very well if your surface can handle the abuse. A small metal plate or piece of plywood can be a handy buffer and you can use the bar under the fork reliefs of a pallet
There are many little moving aids used in the industrial sectors to move machinery, etc. For some unknown reason, I don't have any! If there's a HF version, it may or may not be good enough for occasional use.
If you're patient, creative, and determined, there's little you can't move. Just make sure you can always control the load somehow, especially on ANY slope, you always have an escape, and stay out of pinch points. Heavy tipping things can be fatal. Think at least twice before acting once. Have help nearby or at least a way to summon help on you in case your thinking and precautions fail you. Your spouse can be away for a very loooong time when part of you is pinched to the floor.