I've got the XVT373SV, but I don't see any option to switch between wired and wireless. However, mine is only setup for wired. If you have both defined, I would expect it to give you an option to choose which one to use. If not, I would expect it to automatically choose the best connection which would normally be the wired connection. If the TV doesn't allow you to change the connection, I think Guided Setup would probably be your best option. You might have to scan for channels again, but I don't think it would mess up your picture settings and stuff.
The following might be worth a shot:
1. Disconnect the ethernet from the TV
2. Unplug or turn off the TV
3. Turn off the router or block the wireless mac address for the TV
4. Turn on the TV
5. If the TV can't connect via wireless, it might give you an option to delete that connection
Thanks for the response. There is an option for a wired connection, but as soon as you establish a wifi connection, it is grayed out and inaccessible. I'll try the sequence you suggested and let you know what happens.