AS for the wire, it depends. Which wire? Is it a wire going to a light form the decoder, is it a wire going to a light from the decoder but broke in the middle?
Give a little more information and I, and the rest of the community, would be glad to help.
If your dad is good, and has a good soldering iron, you can fix it. But if you dont, then look into a TCS decoder. They are about $20 and are fantastic.
Then get any NMRA 8 pin decoder. That will fit in that slot. TCS, Digitrax, and NCE all make 8 pins that woudl work no problem. And they are all cheap.
You can also hard wire decoders too by throwing out the board and directly wire into the decoder, it takes away the need for 8 pins and 9 pins like this photo
Right, you can get any 8 pin plug and play decoder and it will work with your locomotive. What Azervich was saying was do a way with the 8 pin. You could do that, but its more work and might be out side of your skill range. So look up any 8 pin plug and play decoder out there and it will work with your locomotive.