sump pick up isnt easy but not hard,

exhaust, starter off,cambelt off,bottom pully etc empty oil out, sump off

if you change the oil pump, you have to undo the engine mount bolt in the drivers side wheel arch to allow room to slide off oil pump

undo oil pump bolts off, undo the pick up pipe, allen key bolts, theres a gasket in between this could of just slipped out or maybe old and leaking, if is, that will be your problem.