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.
On average a head gasket replacement will take 7 to 9 hours labor plus parts. This is a good figure to use however, most vehicles that have a blown head gasket are quite old and you should use the cost of doing the job to consider whether it is better to replace it at that point.