The time varies with the size. Usually a ham can be anything from about 10 to 25 lbs. Different recipes call for different times, usually about 1-1½ hours per kilo. Also, different people like differently cooked hams, 74 C is enough, but some go all the way up to about 83 C (using a meat thermometer). I think I went to 78 C last year. I used one of those plastic bags to trap the moisture in the meat.
The skin didn't get all that crispy, some also like to put a crust on the ham, others rub mustard on it, and some just go plain.