| Hi Button,
The bolt you have circled is one of about 10 to 12 which secure the sump (oil pan). I have recently changed my sump gasket and had to remove this bolt to get the sump off.
Its really easy to fit the sump gasket but time consuming - 4 hours is reasonable if you're good with tools.
hope this helps, the gasket costs about £18 from bmw. | 
