I have invisible fence. But only because my parents in law and sis in law have it. That way we can watch each other dogs.
Invisible fence is probably the most overhyped, expensive system I have ever seen. If you use them, haggle. They priced us out at $2500. When we were done, we got down to under $1000 including install, and I still think we could have gone lower. Basically it is an RC car transmitter with a bunch of wire, nothing sophisticated at all.
We have a small city lot. My parents in law have a small rural lot. And my sis in law have a large suburban lot. None of them have signal problems, and that includes in rain and snow. We had the guy route ours through the flower bed, and he cut a line across the driveway right to the front of the porch. We can let the dogs out anywhere and they can hang out with us on the porch if they want. The dogs don't touch the flowers and are scared of the boundary.
The system works very well. The collar can be set to beep first, then shock, or you can set it for shock only. If the dog sees a bird and chases after it, the collar might beep, but not shock until they are through. You can set it however you want.
The system lets you know if there is a wire break. And they do have addons, like backup batteries. We didn't go that route, the power has never gone off in our neighborhood.
Now my parents have an offbrand unit. They have a large lot. They bought a large amount of wire and borrowed a sidewalk edge trimmer. They ran the trimmer along the property line and around the pond and were able to do it themselves for a much lower cost. They had some problems initially with a line break and low power, but worked out the bugs. You can use an AM radio and a choke coil from RadioShack to find the break. They have a huge dog also, and the dog often gets shocked but sometimes goes right through anyway, usually after animals. Then she doesn't want to go back in. They also have a much better remote, and can manually shock the dog at different power levels for barking or training.
Thats the jist of it from four different households.
To train the dog, you put up flags around the border. They dog wears the collar, with the shock prongs capped off. You walk the dog to the border, when it beeps, you pull the dog back. You do this for a few weeks or until the dog learns. When the dog gets used to the system, you remove the flags. For us, the flower beds and the driveway edge works as a nice border.
Sorry to hear about the dog too. We love our dogs, I bet my wife would be hysterical.