Depends on plugins and skins. It would be a new installation using the same database so I imagine it would keep any settings that are set in the database, but any 3rd party plugins you've loaded into your site would need to be installed to your new environment.
I did a quick search for some of rl's old posts but wasn't very successful.
There should be information available concerning upgrading/migrating at joomla.org
Being a feet-first kinda bloke, I'd backup the database and manually install the newer version into a test.domain.com subdomain, then edit the config to point at the existing database. Browsing to test.domain.com will show any differences you'd need to fix up.
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