If you get too much oil in there or rely on the Dealer to change it during a service warranty, you'll need it. An o-ring won't stop a blowout, the crotch cooler won't entirely either but it will keep it from blowing all the way out on the highway.
change my own oil. but i've been going to the same shop for 14 years to get all other work done. i'm friends with them, ride with them, have gone on riding vacations with them.
you should see the fatbob on the dyna fourm when did you ever seen gold pipes on a harley lol harley is going after the young kids chrome days are over