iTunes Sync & Authorised computer questions

Hey All

2 questions for ya'll..

Firstly -
I got a new MBP but forgot to backup & sync on old MB before moving over. If I sync with iTunes on my new one, will I loose all messages and contacts etc.
I have all the media, apps etc but its the messages that I'm concerned about. I have the contacts syncing to Google too so no biggy there. Just the messages.
Also - As it will be a first Sync, it'll obviously un-jailbreak the phone?

Wouldn't mind upgrading to iOS 6 anyway, anyone else done it and jail broken successfully, I've searched already and saw some people successful, others not (iPhone 4 by the way).

Second main question...
I've had countless laptops, macs and MacBooks through the years, I've forgotten now on 2 of them to unauthorised the computer on iTunes before wiping them and selling them.

So my current MBP is now the third (and last) authorised computer.

Does anyone know of a way of removing them without having the computers ?

Thanks in advance for advice !

guil

syncing will only remove the media, messages will be fine and it won't remove the jailbreak either, to deauthorise a computer click on store in itunes and then view account, from there you can deauthorise all computers and then authorise the current one