'm considering migrating my current site (static web pages) into Joomla!. I rank pretty high in all 3 major search engines and do not want to lose these rankings, what do you suggest? Should I go for Joomla!? Should I redirect the highly ranked pages? I'm a bit worried but my site's growing and I need some kind of CMS. Any other option?
You should definitely redirect the highly ranked pages. However if you are literally just going to create another static site, Joomla is probably a bit over the top. You could use a much simpler CMS for the same task. I use WordPress for this myself, but there are many other options as well.
If are requiring the extra functionality of a full blown (bloated) CMS like Joomla, then go right ahead. But if you don't need all those extra functions, then a simpler one will likely be easier to theme, easier to use, will run faster and have less potential security holes.
I would personally leave the high ranking pages alone, and if you want to integrate Joomla, or any other CMS, then use that to create/manage new content. I'd imagine older content doesn't need too much management really anyway. As a general rule, I try and leave well ranked pages alone, but if it does have to be changed, then 301 redirects are definitely a must.