1997 Honda Civic valve guide seals

We had our motor replaced 6 months ago, they took out the 1.6 and put in a 1.5. Now in the mornings it gives a little white smoke, and has some oil in the radiator, it had an oil leak and they mechanic put some dye in the motor, and the leak is gone now, but the smoke is still there, he says that the valve guide or valve stem seals are bad, so we are trying to figure out, how would he replace that. We were sure that the head or head gasket was bad, but he swears it is not. Isn't the valve guide seals inside the head? If not where are they, and how would they be properly fixed, and what all would need to be done to do it correct?