Seals.To the best of my knowledge, the valve seats on Briggs engines are not designed to be removed. Personally I never replaced one. I have staked them back in, as a last resort, when they have popped out due to overheating. Normally replace the head, on OHV, or short block on L-head engines.
Never had a problem using the 3/8" six point socket but of course I don't go hog wild installing the seals either.they make a special inexpensive tool for the seals that will not distort them like a socket will. If your engine is leaking oil it may be caused by excessive blowby which may be a leaking head gasket. Oil seals these days last a long time if left unmolested or until the valve guides are worn out.