Yes it will. Most control panel software requires installation on a clean unmodified operating system in order to be installed and work properly.
All droplets on DigitalOcean have SSH and SFTP access by default. You can use a client like Filezilla to connect to your droplet and browse/upload/download your files. To do so you will set up a new connection as follows:
Host: [Your Droplet's IP address or domain/subdomain]
Logon Type: Normal
Password: [your droplet's root password]
One control panel that can be installed on your system without starting over would be Webmin. This is a fairly basic control panel designed more to ease the work of sysadmins than to create a user-friendly portal for end users but it will likely do much of what you need as it includes MySQL and Apache configuration tools as well as a file manager.