My expertise is in:
I co-founded a successful digital marketing agency called Crawford and O'Brien LLC (just google it). I like masterminding with high level players. That's why I joined this site.
No, re-designing it would actually help it because it's showing Google that you're updating your content and prividing a better experience for the user - assuming that your re-design is actually a great design. I would recommend using WordPress. It's similar to Joomla, but much better and you'll find more design options. WordPress has a lot of great themes (templates). As long as you're not deleting content and pages - then you're rankings will be fine. Just make sure you do it within a few days time. You don't want a website in progress for a month. But the link juice flows to the domain, so you're fine.
Charles is great. Our conversation consisted of discussing vertical markets versus paid advertising agencies. Charles openly discussed the advantages to the vertical market platform. Charles referred to Crawford and O'Brien's slogan, "Dominate your niche." He effectively communicated select SEO secrets, discussed when paid advertising is appropriate, and discussed Crawford and O'Brien's client relationship duration. The vertical market client to agency relationship lasts much longer.