How long do you to cook 7 lb fully cooked ham?
If it's fully cooked you can either cook it long enough to heat it up, or just eat it cold.
If the ham is fully cooked, there is no need to cook it any further. You could serve it just as it is...even cold. You may wish to heat the ham before serving it, but that shouldn't take very long in the oven, maybe an hour at 350 degrees. The crock pot could take a lot longer and would over-cook the ham.