A Quick Question - help needed!

I've been wondering recently about changing this blog from the template format to the layout format. As I've been blogging here since March 2005 I'm still on the template format but I'm noticing more and more what the layout format has to offer. There are so many pretty blogs around at the moment with lots of lovely additions that I can't put on mine because I'm not on the layout format. I also have some followers whom I can't show on this blog. When I try to add them the instructions are to change to the layout format but it says that in doing so I may lose some changes. I'm struggling to understand what that means and fearful that if I press the key to change I may loose everything. The other alternative is to start a new blog but I don't really want to do that as I want to keep this one all together. Has anyone changed from the template to the layout format and if so - how did it go and what, if anything, did you lose along the way? I'd really like some advice on this.