I used your tutorial to install. Thanks for providing BTW. Was not sure how to update though, i tried "sudo apt-get update mediacenter21" but it did not work. At the moment i am running "sudo apt-get install mediacenter21" i am fairly new to linux and was concerned that this would install another instance of MC instead of updating it. But it seems to have updated. All good.
Not sure what update manager or synaptic are (gui based?), so far i am doing most things via CLI.
Thanks
"apt-get update" only updates the list of what apps are available (syncs the repos). "apt-get upgrade" or "apt-get dist-upgrade" are what actually updates the software on your machine. So you need to do the "update" for your system to realize there is a new package available, and then "upgrade" or "dist-upgrade" to actually upgrade the package. Using apt-get install just reinstalls the software, which, if you've already run update will have the effect of upgrading the software, but can have side effects.
Awesome Donkey's command line is the correct one to do a global system upgrade (including MC), which you should do regularly for security reasons if nothing else, but I thought it might be helpful to understand what the commands do.