Good SEO Ranking - But needs rebuild

[mixer25]

I currently have a website doing really well in search engines with a google rank of 3 and generally gets good hits.

My concern is that its dated and I am going to totally change the site with new ecommerce software, which I am worried will destroy my rating or have to start again in google.

How can I prevent this the best way?

Thanks

[princess]

what kind of change are you talking about?

[mixer25]

same content, i.e same products but totally new software, so all pages will be reindexed, new site map the lot...

What do you think?