I was just thinking the other day, that my site is starting to look a little tired. I don't need a super fancy 'latest greatest' type of site. In fact, I actually prefer a more old school site. But... The biggest problem I'm seeing is that the site has become sort of like a house that has been added onto, too many times. Slowly adding products and info piecemeal over the years, has created a less than perfectly organized situation.
So my question is... How bad could the damage be from a total rebuild? SEO? Broken links? I actually get a lot of biz from word of mouth referrals on forums and such. I'm worried what will happen when all those links potentially break. Though I put virtually no effort into SEO, I still do quite well on product keywords. Something I obviously don't want to loose.
Also... Are there any really good template type builders out there, which offer a lot of flexibility, but don't have a big learning curve? I use to code my first sites by hand, then used DW. But I just don't have the time anymore. I would like something that is easy to allow change.
There is really no reason to generate a 404. Your old links should point to new ones using a 301 redirect. If you are using php, look into ModRewrite. Any links from forums, etc should still work and point the "new" page.
There's no need to have broken links. 301 redirects are your friend!
Do some research now to list all your existing URLs, so they can be properly redirected to the equivalent new URL when the time comes.
Also do some research to identify who is presently linking to your site. In some cases it would make sense to ask the referring site to update the URL. In other cases it would make sense to leave the link alone and let the redirects take clickthroughs to the new location.