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 can say that since I am now familiar with it, it would take me about 4 to 5 hours to disassemble, replace the gasket, and reassemble. A mechanic should be able to do it in around 4 hours easy, but it all depends on how hard it is to access your engine.