You could easily use the Obi100 if you wanted. The analog port is only useful if you plan to keep your existing home phone line or want to connect a service that uses a phone port to connect like the following.
NetDuo <>Magic Jack <> Ooma <> FreeTalk (Skype adapter)
You said you want to port a home phone number. It may not be possible. There was a restriction on Google Voice porting where only mobile numbers could be ported. In some cases it still may be possible.
So far as the process of porting a phone number the first thing to remember is Don't cancel your phone service until the port is finished. If you cancel before you could lose the number.
Here is another users experience porting to give you and idea of the process. The reason he ported to prepaid phone first is because Google won't port a land-line phone directly.
http://www.obitalk.com/forum/index.php?topic=1051.0