I have a 1998 F150 V8. Whenever, I accelerate from a stop the oil gauge needle drops all the way to the bottom, but rebounds rather quickily, pretty much drops and back to normal pressure in 1 to 2 seconds. I am thinking the gauge is bad or the pump is going bad. At cruising speed there is no drop in pressure. at idle there is but again a quick drop and regain.

If it is the oil pump that needs replacing how hard is it to remove the oil pan and pump?

First put on a real oil pressure guage and test. You may just have a bad sender or guage.