What are you trying to do with the wifi connection? It can take internet... but... it isn't going to run an MD.
Your user account password is your user account password. If you are typing sudo ANYTHING (sudo echo "echo") and it is refusing it, you are typing it wrong, your caps lock is on, or it was on when you installed. That isn't something we affect at all.
Probably more importantly, unless you had 2 findable nics installed during install... you have a single nic configuration, and trying to use one as wifi (again, fine if you are just getting internet) isn't going to happen. You will need to reinstall. Check your /etc/network/interfaces file to see if it has an eth0 and eth1 or if it is eth0 and eth0:1
While in the installer (when it shows you the reboot now button) you are going to need to work out your whole wifi situation. ctrl alt f2, type sudo -i, and set everything up by whatever you are following. I have a thread on here about how to do it. Once you get it working correctly... copy the files you have created to the appropriate directories under /target/ making sure what needs to be executable is, and that it is set to load up at boot, so that the first boot script can ascribe the wlan to be the external interface, and download the needed bits.
OR, conversely you can take internet in on the rj45, and then once it is setup and you can get into web admin, go to networking and select the swap nics option and update/save... after setting up your nic to work correctly.
In any case, none of this is an expectation for a server/router and is unsupported... but I am happy to try and help where I can.
Also... if you ARE going to reinstall... use the latest snapshot.http://linuxmce.iptp.org/snapshots/