I can not believe a so called mechanic/ technician (is what hey call themselves nowadays)? would even contemplate opening a rad cap after a car has been running , as for hard hoses, they will feel hard as they should be, im not sure about the Z but most will be holding around 10-14 lbs, to increase the boiling point of water. As for head gasket there are a couple of things that can be done other than the visual things you have been told about, when i used to work in motor industry, there were some dye tests that were carried out on a sample of water taken from your cooling system, looking for high hydrocarbons in the water which can only get there from engine gasses,
Another thing i used to see, was a sniffer test from a exhaust gas anayliser, they used to hold it above the rad cap , run the engine upto temp untill thermo opened, and the probe could pick up hydrocarbons as the water circulated. confirmed a good few that way in my old times. it may be completly different now tho and may not work , oh how i miss old school mechanics/ engineering i