Format, reinstall, Upgrade?

I'm intending to format my MacBook Pro and reinstall OSX Lion, then upgrade to Maverick. I have been using the laptop for many years and it is quite a mess so i'm considering a completely fresh start to be the best option, rather than try and clear it up. Is this the wisest option, or is there a way to format and upgrade at the same time?

Also, i'm concerned about a few things. Firstly, i presume my iTunes library can simply be copied to an external drive and reimported, much like my documents? Secondly, i understand my iPhone will see the MacBook as a different computer after the format, how can i avoid this and make it sync as usual?

Any help appreciated

If it is a mess, backup to an external drive, download Mavericks, if your MBP can meet the specs. Before running the Installer burn to a USB thumb drive, boot from that, format the hard drive and then run Installer, update to OS X.9.1 and use Migration Assistant to bring things over.

Ok cool, i will do that. Thank you for the advice. Regarding the iPhone, will migration assist move all of the phone's details to the 'new' computer? I'm hoping i can just plug the iPhone in and it will just sync as usual rather than thinking i've plugged it into a new machine and, therefore, insist i wipe the thing...