Just updated BobbyMods to 6.12.
I also updated a couple of multi-site installations, and if you didn't hack core and put the themes and modules where they should go (as opposed to where-ever it works) it should be fairly easy.
In this minor upgrade (Drupal 6.11 to Drupal 6.12) the steps are:
- download the new version
- extract it
- 'diff' this version to the previous version, so I know what's going on
- In this case 6.11->6.12, an overwrite would do AND there are no database changes
- I removed the .htaccess, sites folder and robots.txt from the extracted new version, and made a new compressed file (zip,tar, etc.) from the new version without those files (I checked that they had not changed in ).
- upload the newly created compressed file with the new drupal version (6.12) to the drupal folder of the site to be updated
- extract the new drupal version
- run update.php (optional, no database updates)
- check the status report and site working
For the multi-sites I just keep logging in and performing  (optional) and  after the initial update.
If any of the above items above aren't familiar to you, please follow the instructions from the Drupal 6.12 release announcement.
If you don't have the inclination, or don't know what this is all about, just have someone do it for you.
Only you know your install, and when unsure, make a backup of your database and drupal folder before proceeding.