To get to the "other" part of the post, the seal of the gasket under the cover will not be harmed when that bolt is removed. That bolt is too high to have any fluid drain from it so that is a plus. Even a lower bolt can be removed. That is the best way to drain the oil from the beast any way. If you don't want to drain, then put the bolt back in and snug it down. That gasket is cardboard and glued into place most of the time. Hotrod, good suggestion on the 20 penny nail. That and some vice work will get a nice clip in no time.
