Managing personal Outlook.com account settings, security, and privacy
Hi Visual_Deadlock,
In addition to what Ron Sommer said, please be informed that once you upgrade your account to Outlook.com, your email address will still be the same, so to be clear, your two email accounts will not merge because they are both in different account name.
All your contacts, emails, files, folders and even calendar will stay on your account. Outlook.com is just an interface, you won't lose any information/file if you upgraded to Outlook.com.
Regarding your concern with renaming your account, the Rename feature is currently not available. The Engineering team is aware of the problem and working to fix it. At this time, we don’t have a date when the feature will be restored. We appreciate your patience.