I second what alpac said.

It sometimes seems difficult when you open the hood and see a mess of hoses and mechanicals but it's just an engine like any other car. Start with a simple DIY oil change, the BMW I-6 is one of the easiest engines to do this on. IMO, the thermostat and the water pump are extremely easy to do since there is no timing belt to remove unlike many cars. Forums like this make everything so much easier too since others have tackled the same things, Google is your friend.

When it seems intimidating, remember this: Someone put it together, I'm pretty sure I can take it apart. You can always get help to figure out how to put it back together