You don't have to answer his question regarding the woodpile. Simply reiterate that it's on your property, and he needs to move it. Period. It has nothing to do with anything other than, he's encroached onto your property, and is not entitled to do so.
If you're considering a fence, maintenance depends on what type fence you get. If you get a barricade type fence, set it back on your property the width of your mower, so you can do 1 straight swath down the fenceline on the outside of the fence. This allows you to go straight in, and back straight out. It also affords you the ability to weed whack the outside. If you get wire/chainlink type fencing, only maintain your side of it. If he doesn't maintain anything along the fenceline, and it gets out of hand, get some weedkiller, and spray a thin swath along the fenceline. With it being wire, it will go to his side too, and that will take care of the problem.