Root access is the same regardless of the control panel, you are correct.

You should ask your ISP about their web server policy in detail. My ISP doesn't allow web servers but they don't block port 80. I called them and asked about running a web server for a family site and they said that would not be a problem.

This would be a good way to play with a few of the bugs before you go with the dedicated.
I think the cheapest you will find will be something like Managed.com at about $55/month plus whatever they charge for cPanel. cPanel is certainly the best control panel from a customer point of view (imho) but it has a history of security flaws. That would be good to keep you on you toes while learning the server management end of things.