If you had an amp its probably under rear passenger side seat. mine is on my 99 with infinity.
the three wires in question will be no connect. If the new head has a wire to light it up with oower off, you may want to connect one of the to in question from the jeep wires to new head. The instructions or wires should state one is for 12v key on and another for 12 v constant. maybe another for lights. Get a meter or lamp on two wires and play with these two and see how they behave.
The wire for remote amp comes on when the stereo is on. Its purpose in life is not to power an amp, but to remotely turn it on. Power to the amp itself is best provided by its own heavy wire going straight to battery + with a fuse at the battery end. More important for hi watt amps.
You could use that wire for the amp to power anything lo power. disco ball?
If you can return it, get one from crutchfield. They come with a free install kit, instructions for your exact vehicle, and phone support. Plug and play, they give you an adapter harness. I know car stereo, but why think when I dont have to ?