How Do I Transition to Membership From A Different Site and Plugin

I am switching over from one website to another. The old website had Premium Members using Paid Membership Pro as the membership plugin. Presumably most of these members will continue as Premiums at the new website. I will be using your Membership plugin on the new one.

Those who come over are being asked to register as Regular Members under their same email addresses so I may identify them (there are not too many). I then plan to manually upgrade them to Premium Members for a defined period of time (say a month) when this membership will be downgraded back to Regular Members and they will be asked to upgrade through the Membership Plugin should they wish to continue their Premium Membership.

Three questions:

1. Will my approach work as simply as it appears to me or am I creating unforeseen problems (for me or them)?

2. How do I upgrade them manually and then downgrade them manually?

3. I presume once they upgrade via Paypal that Paypal will signal the system to upgrade them. If they discontinue their membership once in the system, does Paypal automatically signal to Membership to downgrade their membership? Is all of this management transparent to me (other than email notifications) and not need any intervention?

Thanks for your prompt response,