First off, you wont get shocked. The system is only 12 volts.
Second, disconecting the battery will not kill the engine. The Battery is only used for starting the engine. Once the engine is stared, the alternator will supply the electric required to keep the engine running. A car will run n a dead batter, but it will not run on a dead battery and a dead alternator.
As for killing the engine, there are a few things you can do. The only problem with shutting the engine off, is that the electrical system will remain on because the igniion will still be in the on position.
Tripping the fuel cut-off switch is the easiest way to kill it. It will die within 3 or 4 seconds once the line pressure bleeds down.
Once the engine is off, disconnect the negative battery cable to shut off the electronics.
Either take it somewhere to get it fixed, or go to a junkyard and buy another ignition switch, if that is the problem. A multimeter and a wiring scematic can help you diagnose the problem.
Tom
BTW, do you realize that her Explorer is 19 years old? How many problems has she had with it? How many miles are on it? Just wondering. It is really rare to see a 20 year old "junk" American car on the road. Here in Ohio, they are all over the place since the Japanese cars of the 80's tend to migrate back into the dirt as iron ore. (Rust to death) I am just wondering.