Migrating Address Book dilemma with iCloud

I'd be inclined to delete the contacts from the Phone before beginning. I'd migrate to iCloud on the Mac and then log in to the account on the phone, electing to merge your contacts when prompted.

If you are at all nervous about the process, perhaps a good first step would be to make a backup of the contacts on your Mac, you can do this by exporting from the file menu.

The easiest way to delete the contacts from your phone, would be to delete the mobile me account itself. You can do this from settings> mail, contacts, calendars, selecting the MobileMe account from the accounts section, scrolling down and hitting the delete button.

You can log into your newlyformed iCloud account on your phone through settings> iCloud, simply enter your ID and password. You may not be offered the option to merge on your phone, because you don't have any contacts on it (after deleting them).

If you have a Time Machine backup, you already have a backup of your mail. However if you wish to create just a backup of your mail (on your desktop say), you can do so by clicking on your desktop and then going to the Go menu in the Finder and while the Go menu is displayed, hold down the Alt key on your keyboard. This will reveal your library in the menu, which you can then click to open. Control click on the mail folder that you see within the library, and choose copy Mail from the contextual menu that appears.You can then control click on your desktop and choose paste item from the contextual menu that appears to have picked your mail folder to your desktop.

As iCloud, (if you wil) is the master copy of everything and is held in the cloud, by initiating iCloud on your MacBook you have already sent the data to the cloud from the MacBook by choosing the options you wish to use in system preferences > iCloud. The data in the cloud will then be written to your phone based on the services you choose from settings > iCloud on your phone.