Oil pump housing leak

Oil pump housing leak.
truck leaks during warmups only.
no drivability issue.
i previously thought it was oil pan leak, and fortunately I haven't done a gasket replacement on the oil pan yet. The temperature in michigan felt cold. I finally got the courage to crawl under truck, and that's when I discovered the leak was from the housing to block ( bleeding at the seam), with engine running.

i looked in the Hayne's manual and I was discouraged by the repair procedure: manual says the oil pan has to taken off. The crank pulley has to be removed. I consulted with a mechanic friend, who will be helping me on this repair job: He stated that the crank pulley did not need to be removed ( and I thought that would be great!). I forgot to ask him about wether the oil pan needed to be removed. But looking at the diagram in the Haynes manual, it looked like the the crank pulley needed to be off.
will you kindly tell me all I need to know and all I need to replace ( is there anything in addition to the housing to block gasket that require attention?). I don't know if the oil pump housing leak was there before I replaced the camshaft seal and timing belt about 2 weeks ago. But I know my floor jack slid off at one point while supporting the oil pan, and the oil pump housing is immediately above the oil pan.
i'm extremely grateful for as much information/help as you can provide me with.