how to change oil pump

You need sufficient clearance to remove the oil pan. This will depend on the clearance between the oil pan and subframe. Ford and chevrolet are pretty good about allowing clearance in their truck and SUV models. A good rule of thumb is you need as much clearance as the oil pan is deep on the shallow end. The deep end is where the pump is, and normally, on longitudinal engines, the deep part will just hang down and the shallow part is the only thing that needs clearance.

The oil pump may be located on the front of the engine - if V/8 ... The oil pick-up tube is inside the oil pan .. Engine size is always useful info.