Answers to questions
1) by default you will be able to use sftp to transfer files
2) it depends on what you want to know... try 'man ssh' first and if you find something that you're interested in google it
3) if I understand what you are asking correctly then openssh is already setup to authenticate system user's passwords
4) for windows sftp transfers I use filezilla. just enter the address of your server and set the port as 22 (or whatever port you may have set for ssh) and thats it!!!