In addition to Paul's answer.
You will have to make sure the pages are unique in terms of meta title, description and content. Duplicate tags are bad and can lead to lowering your results.
A site overhaul brings many points of attention in respect of not losing any built up link juice. Make sure you make permanent redirects (301) for your old pages to the new ones.
You can get penalized trying to fool google. Better not try that. But hard organic work will usually be rewarded but takes time unfortunately.
