Of course you can use a wireless handset (I am doing that as well). What you get is two standard telephone jacks where you can connect everything you would connect in a traditional phone jack.
On the LAN side you need an Ethernet Cable connection to your hub/switch/router. You could very well use a wireless solution (not USB) if cabling is not possible. The cisco has a DHCP client integrated and will automatically resolve an IP Address from your NAT environment.
This issue is known because the 64k codec can only be used at ONE time. The other side must be configured to a lower codec and it should work. But configuring an ATA is not an easy game because all the settings must be defined in binary (value 1 or 0) and then entered in hex format. The cisco guys didn’t bother about normalos and didn’t set up a web configuration menue. Instead they (respectively the company who developed the box) chose the HARDCORE version to confuse everyone. Reading the 500 page handbook is also not as much fun as reading the TIME magazine. I am ONLY able to copy and past configurations given by a telephony provider but I am quite happy with that and don’t need more. Have a look at http://pulver.com/fwd/quick/nat-ata.html
Freeworlddialup will ease up your peer to peer connection with ATA, free of charge.