How does a GPS unit work?

What is the chance that my portable Magellan Crossover GPS unit can be repaired or work again?

• The unit has been used very little, even though it's about four years old. It was working fine on a cross-country trip last month when it stopped functioning in central Texas. Now it won't go past the Warning/Disclaimer page when you turn on the power. It does this when using the power adapter plugged into the cigarette lighter, the built-in battery after it's been fully charged, or the A/C power adapter indoors. I'm guessing that it's toast and that it would cost almost as much to repair the unit than it would to buy a new one. I'm thinking of buying an iPhone anyway, which has a GPS feature. I know it's not the best GPS available, but it will probably be sufficient for my needs. I welcome all answers or suggestions.

• Answer:

  It probably can be repaired, at least by a technician with the proper service literature and parts access. But, as you consider, it may not be economcal due to its age.