Chevrolet Repair: 83 Chev. Celebrity, head gasket leak, combustion chamber

Question
I have a chev. cel. 2.8 6 cyl. I recently had a water pump replaced and two of the small bolts broke off the mechanic retapped and replaced the bolts. A couple of weeks later I noticed the radiator a couple of cups low but nothing on the floor I was told this could be the head gasket leak, how can I tell if this is a head gasket leak and how long can I drive it this way. I have filled the reserve fill tank about half but It is not going in the radiator.
Thank You  

Answer
A leak in the head gasket will usually cause one of the following.

coolant leaking into oil - is your oil a light tan color ?

coolant leaking into the combustion chamber - do you see white smoke or
are you over heating ?

coolant coming out of engine at the head - you said no coolant on the ground


check your radiator when it is cold and refill at the water pump.

it is possible that you have a small leak somewhere and have not seen it yet.
it is also possible that it was not completely full when you picked it up.