Hi solarisc ..
Welcome to the Mac community! I know you will have many hours of happy computing ahead of you ....
I'd like to present my views on your question ... other's may vary ...
You may choose to not apply any new updates and just keep things the way you have them presently .. which I assume is a version of Tiger.
There are many users of Mac OS X still running earlier version of OSX like Jaguar, or Panther .... and are very happy with their systems ... They may want or need to install the occassional security update but that's all ....
There are 2 types of updates ... security updates and system updates.
Tiger is at a very stable version release .... so it may not be necessary for you to consider applying any more updates ...you could for example install only the security updates if you wanted to.
Leopard will be along soon and you may just wait till then and "upgrade". Or at that time the system updates will have all the bugs worked out of them and you can update then. For example, now I'm running the last and latest update of Panther ... version 10.3.9 ... but for the longest time I just stayed at 10.3.6.
The other thing to do is if you want to keep current with all the updates ..
wait for a week or two to see if there are any major issues with the updates. You can read about them on one of the numerous forums ...
If you have to "backtrack" to an earlier version of the OS ... here is how you do it ...it's really quite easy ...
Archive and Install
http://www.thexlab.com/faqs/archiveinstall.html
Then install combo update of version you want to revert to ..
Standalone Installers ...
http://www.apple.com/support/downloads//
Some general advice before doing an update ...
Before any system or security update ..
1. Disconnect all peripherals except keyboard and mouse ..
2. Make sure sleep and screensaver are disabled ....
3. Quit all other apps ..
You should also make sure you are repairing permissions on a regular basis. This is a great app for doing that and a few other things ...
Macaroni - Just Set it and Forget It!
http://www.macupdate.com/info.php/id/9633
Here is some more info for you re: Updating ...
The X Lab - Why Update?
http://www.thexlab.com/faqs/installswupdates.html
Keep this app on hand for troubleshooting ..
...Onyx
http://www.macupdate.com/info.php/id/11582
Go to Automation Pane ..
Check all the boxes EXCEPT
1. Optimize the system
2. Hidden DS Store Files
3. Links between documents and applications
Also choose "Clear All" in the button box for caches. Then execute
These settings perform three basic troubleshooting procedures ...
1. Repair permissions
2. Run Unix maintenance (cron) scripts
3. Clear caches
With Macaroni and Onyx ... you can eliminate almost all of the few problems users might run into ...
For the ultimate in protection I recommend
Disk Warrior
http://www.alsoftinc.com/DiskWarrior/index.html
And don't forget to back up!
SuperDuper
http://www.macupdate.com/info.php/id/13803
Carbon Copy Cloner
http://www.macupdate.com/info.php/id/7032
iMsafe
http://www.macupdate.com/info.php/id/8874
The X Lab - Backup Advice
http://www.thexlab.com/faqs/backuprecovery.html
Cheers!