Hi Barbara,
I have been designing and updating websites for almost the last 9 years and I first learned Dreamweaver when I was in school. While it is a great tool for some, I find that Dreamweaver tends to add a lot of unnecessary code to the web pages -- so while you can most definitely work in Design mode as mentioned above, it is a very good idea to have a good understanding of HTML and CSS too. In fact, I think that is probably where you may want to start.
VAF has had several chats that teach HTML and CSS. Here is a link to the Website Coding section of the forum:
http://www.virtualassistantforums.com/website-coding
Once you have a good understanding of HTML and CSS, then working in programs like Dreamweaver will be a walk in the park

Actually, if you obtain a good solid knowledge of HTML and CSS, you won't even need Dreamweaver to make website updates. I never use Dreamweaver to do this type of work.
Good Luck and congratulations on the business lead.