Put 5060 as value for SIP in both ends.
The two units negotiate through SIP what portnumbers should be used for control and audio,
so you will need to get SIP running before anything else will work.
Only if you have IP telephony at either end, that uses the 5060 port, will force you to use another port for SIP.
The DynDNS service that you sign up for and are free, I belive only reports what IP you have externally and some people use the remoterig for that. It says on the status page in remoterig what external IP you have and you'll need to set that IP at the other remoterig as other party.
If you choose the advanced DynDNS service that you pay an annual fee to get, I believe it handles your dynamic IP correctly and automaticly without you having to set it manually in the boxes each time it changes.
Ubbe.