How do we Update/Upgrade Our Site & Not Lose Google Rankings?

[daddyoh]

The site is a bit over 2 years old & PR3 with a few PR2 inner pages.
I read that changing a site could lead to a drop in the SERPs.
We want to add a way to sell our inventory from the site, like a Shopping Cart.
We also want to do a radical modernization of it...a new look for 2012.
We have many top 5 rankings in google for multiple terms.
Is it possible to make these changes and not lose our rankings?
What dangers do we have to watch out for?
Have you ever done this before and how did
you do it and what were the outcomes?

[Barefoot Warrior]

I'm not going to be very helpful, but ... I've found that a change, even just modifying a few things like images and text, can result in Google dropping my site right off the front page. However, it returns after maybe a few days to a couple of weeks later to a similar or stronger position.

I don't have this as conclusive proof, or at the level you're talking about - just thought I'd get the ball rolling

Patrick

[caseycase]

I have not seen much change in my rankings when making aesthetic changes as long as I kept the content basically the same. Start changing the content significantly, however, and you might see a drop on those pages.