If you refer to "factory reset" on page 10 of the user manual, it shows the steps required to return your TV to the shipped from the factory settings. It should be possible to follow the steps without seeing a screen display as the cursor would normally start at the first option and be directed through certain exact steps as listed to the desired result.

Shut off the TV and pull the wall power plug for about ten minutes (while waiting extract the remote battery and give it a good rub with a tissue on both sides and then reinstall)then insert power plug again and set power switch to "ON" with green led confirmation.

Using the instructions and menu drawings on page 10 carefully step through the given sequence and hopefully things will return to normal.

Good luck!

Here is a link that might be useful: User manual