The first thing that I would do is make sure that you have all of the settings that you will need prior to the switch. Things like email and any connection type settings.

Are you going from a dial up to DSL, or just changing to/from dial-up, or to/from DSL.

The reason that I ask is that the rest of my answer will differ depending on what you are changing.

I will try to check back and see if you have answerd, and hopefully to able to give better advice.