Switching From Pre-Pay to Post-Pay, Add A Phone, Port Numbers?

Hi,

I purchased an HTC Sensation and a $50/mo. pre-pay plan to test T-Mobile's service in my area.  I'm pleased with T-Mobile, so we're going to buy a second handset, want put my wife and I on the $80/mo. post-paid plan, and port both our numbers from Sprint.  What's the best way to handle the plan change and port?

Thanks,

Jim