Mechanic Q: head gasket?

I have water dumping out my tailpipe and i think i blew my head gasket. Car was not running hot,it ran rough a block from my house and i parked itJust replaced the radiator,water pump and thermostat.You guys have been a big help to me,so my question is -Do products like steel-seal,duraseal etc. really work?

Mechanic Q: oil pressure guage?

My oil pressure guage drops to about a quarter of the way to the low side and will go back up when i step on the gas. Is this something i should worry about? car runs fine -thanks Tim

Mechanic Q: low coolant?

how can i tell if my head gasket is bad in my car,recently flushed my radiator,idled a little rough for a day or two.coolant was a little low so i filled it up.car did not run hot.did i do any damage to anything?

Mechanic Q: a/c wont blow cold?

put freon in it,compressor is good,blew cold for 1 hour-what could it be