how hard is it to change the sump gasket and how do you change it?
rear main seal isn't leaking as much oil but still i would like to change them both,
do i have to pull the engine out?

if your doing both it would be easier to pull the engine out..
you can do it in the car but the gearbox and flywheel needs to come of to do the rear seal and the cross member will probably need to be removed aswell...