The invisible fence does not need to be dug into the ground. Ours lays on top of the ground redneck style, and works just as well, though occasionally a deer will trip on it and break it. When that happens, we go outside and repair it. It's pretty simple. We will rent a machine from the tool rental place, that digs a narrow slit in the ground and pushes the wire down into it, and our problem will be solved.
We spent very little money on our fence. We bought a compatible type of wire at a big box store instead of buying Petsafe's wire, and we have taken the transmitter with us when we've moved. We never found ground flags to be necessary. The collars occasionally need to be replaced when the buckle breaks or the receiver gets broken. You do need to keep stocked up on fresh batteries and make sure the collar is working. I check it daily.
The design of the invisible fence is very, very good. The dog receives a warning tone when he gets near the boundary. Until he gets closer, all he gets is a warning tone. If he gets too close(you adjust a dial on the transmitter to decide how close) he hears a different tone - even closer, he gets a slight zing from the collar. My dog has gotten zapped about once, and he figured out what was what from that. He actually walks near the boundary and listens for the warning tone, and he also knows that he can be in the warning area without getting zapped, so he nonchalantly strolls around in the warning area, with his collar beeping away, LOL.
Beware - at least my dog is very aware of when the fence is not working. I swear, he strolls over to the warning area every morning and listens to see if it's on. I am very sure he would wander off the property if it was off for a while.
We also do not leave the dog out and rely on the fence working when we are not at home.
We also unplug the fence and keep the dog inside during electrical storms. There is some chance of damage to household wiring, so we have a surge protector on it where it plugs into the wall indoors.
That is why some people say, rightly so, that the invisible fence gives a false sense of security. Dogs DO learn when it's not working, and one has to check it often. When your electrical service is off, your fence does not work. If you have service interruptions a lot, it's not a good choice. It's best if combined with another form of fence.
Of course, the other disadvantage is that it does not keep other dogs from wandering onto your property.
The thing is, if you take the dog across it to take her out of the yard(say to go biking or for a walk down the road), you are actually teaching her/him to not respect the fence, and the training will eventually get messed up by that.
Some people resolve that by having the invisible fence encircle an area that includes access out the back door, and taking the dog for a walk off the property, out the front door. Doesn't help much when the problem is it racing out the front door whenever it is opened, but the layout of the fence does take a fair amount of thinking. It's also no good to put in a lot of sharp corners in the layout of the wire, or try to have it cover an area with complicated boundaries.
That said, the invisible fence is no cure for a nervous, high energy dog that needs mental stimulation. Anyway, you could have a lot of land, and still have the basic problem. The dog will stand there and bark at a spot on the driveway or stand and bark at the property line all day (or at the neighbors) if it doesn't have some sort of job.
A dog like that needs a job. Obedience, trick training, agility, biking, were mentioned. But depending on the roads around you, tailgating can also be good. A big long exercise session once in a while doesn't tend to work well. A daily routine that includes challenging activities does.