Yeah use PC suite, sync with your PIM of choice then reverse the process.
Sync with outlook... prioritising the nokia.
Then do the same for your SEX, only prioritising outlook this time.
Ps you didn't say which xperia you had? There's more than one you know...
So the x10 will come with software to sync with outlook... similar to pc suite.
Save a backup of your phone via pc suite. That way if it all goes wrong, you can get it back onto your Nokia.
THen use the software which comes with the x10 and do the same.