Here's a step-by-step instruction on how to create a number of site collections, content databases and how to combine them.

The Metalogix BLOBulator tool provides a health check for your SharePoint content database that will give you the knowledge to take action.

Locate the database that has the ginormous .ldf file, and use either of the following sets of steps to shrink the transaction log file down to a reasonable size: ...

But at some point, SharePoint Central Administration showed that the database was "offline" or something to that effect, which finally let me delete the service and finish the update. Woo.