For short periods of time, prescription medications (such as narcotic pain medications or muscle relaxants) may be helpful to alleviate pain or related complications.
It can take anywhere from 4-10 hrs. now if your head gasket is warped you will have to take it to have it milled that takes from 1 day to several days. if not you can just buy a completely new one that fits perfectly for about $150.
I need to replace a leaking GE gas water heater that had a 12-year warranty but only lasted 8 years. This time I want to get something that lasts for, say, 15 years. One plumber I know highly recommends American Standard as the longest lasting, and he also installs Bradford White. He does not like the common retail water heaters such as GE, Whirlpool, and Rheem.