That looks like it has been around. That is an older surpass engine and if it's in running condition it may be worth $30.00 toward your conversion. Does the wing have ailerons ? I see a servo mounted on it's side in the front....not sure from the pics what that would be for.
If you want to convert it to electric you would need at least a Power 46 motor(or equivalent ) a 60amp ESC and a 4 or 5cell lipo.
If you have the equipment lying around I would do it. If you have to buy it I would think twice.