hey i am having trouble with my 1989 rd28 deisel laurel.it seems to use water very quickly and as i look under the car water appears to be dripping out from under the engine rather than the radiator.car will drive about 5min then over heat.suspected head gasket or what?

Try a pressure test on the cooling system. Put some pressure on it while its running the gage should pulsate with a leaking head gasket. A good radiator shop can do an analysis of the system and give you a definate answer.
Even doing the work yourself I would want to be sure before starting.