Is there a service in the that can show me where pipes and wires are buried on the lot of our recently-purchased house?

I've been enamored with the idea of putting in a geothermal heating/cooling system to replace the existing natural gas furnace and conventional heat-pump, but I know this is often infeasible on an existing home. Knowing where I can and can't dig would help to settle the question. :-)

Thanks, -Luke