1995 Toyota Camry engine overheating water boiling over int

my 1995 camry ran hot about 3 months ago. the engine would not restart. my neighbor and i discovered the noise suppressor was the problem, cut it wa lah, the car started again, no more problems. after several months of driving, i noticed the engine began to run hot and radiator fluid was boiling over into the reservior. i thought the waterpump, thermostat was bad. i spoke with a parts store clerk who thought the head gasket may be blown. after research and careful thought, i agreed. i found this product, blue devil. i have not used it. looking at several forums on the i-net, i found some reported a few good results from the product, while others strongly recommended against it (clogging other engine components). my question. it is possible that the head gasket is blown?. considering the age and mileage of the vehicle, is it worth the major expense of an estimate $1500 (+), will using the head gasket product be worth a temporary fix until i obtain another vehicle and lastly, what is the estimated cost of a head gasket repair and what component are recommended to be replaced since the other engine parts will be exposed, i.e., water pump, t-belt etc?
your expertise and knowledge are greatly appreciated.