I know this is an old post - but maybe it can help out someone in the future
I use DW on a regular basis and templates can be time savers especially for large websites.
When you are creating the dreamweaver template (btw I'm going by MX 2004 here) - you will be presented with an option "update all pages created with this template?" (or something along those lines - I'm half asleep right now) - make sure it's checked.
When you create a new page, make sure you create it from that template. So when you go back and edit the dreamweaver template it will prompt you - update all pages using this template (or something along those lines), you will then have the option of saying yes or no.
Now for the snags - sometimes you will get a couple error messages, sometimes you created an editable section when you really didn't want it to be (editable sections don't get updated) and sometimes DW will act up.
If you're receiving a specific error message or having trouble actually setting up the inital template - let me know and I'll try to help out any way I can
Regards,
Teli