Planned upgrade from Shared to VPS!

[shytom]

Hi all, been with hostgator for nearly 2 years now and I am looking to upgrade from a Shared hosting plan (Business) to level 3 VPS with cPanel so I can offer more features from my website but need to ask some questions before considering it any further.

1 - I currently use Hostgators Registry Rocket to manage my domain name - how would I go about creating Private Name Servers via the Hostgator Registry Rocket service?
or do I need to register the Private Name Servers with another Registar then just update the DNS Information page once done?

2 - Can Hostgator move my existing web site and files over to VPS so it is already to go and my website is still online while I get to grips with everything behind the scenes?

3 - I currently pay monthly via paypal upon receiving the invoice, do I continue to pay the exactly same way as I have done since becoming a Hostgator customer?

4 - If I need to upgrade to a VPS Level 4 or above in the future how easily is this done and will my site suffer any downtime while the upgrade is happening?

5 - I am kind of new to the server side of running a website, is the learning curve for running a VPS after being on a shared hosting plan very steep?

As I know the Hostgator Staff are very busy and can only browse the forum when they have the time to, any help from anyone that has moved from a shared webhosting plan to a VPS plan or has knowledge about this kind of upgrade would be great.

Thanks in advanced for any help