Port forward Edit
You can forward a port on an SSH client through an SSH connection:
ssh -L 1234:localhost:5678 username@host
Here it forwards port 1234 on the client to port 5678 to "localhost" from the SSH server. This means that you could replace localhost with anything the SSH server can reach and effectively forward to anything on the SSH servers network.
SSH key Edit
For details see the SSH Key Authentication article.
cat ~/.ssh/id_rsa.pub | ssh $HOST "cat >> ~/.ssh/authorized_keys"
Server port Edit
You can change the server port by changing the 22 in /etc/ssh/sshd_config on the line that says: