You are going to like your smartcraft display once all the components are working for you! It provides a wealth of useful information. I installed a system in my formula 353. Be sure and consider adding as many functions as you can afford. To me, the steering sensor is very helpful. It is so easy to point those drives straight ahead for slow speed movement and trailer loading. Here are answers to your questions:
1. If your boat only has one tank, use tank wire 1. Cover up and do not use wire 2. Fuel comsumption monitoring is done through engine sensors not fuel tank level sensor.
2. The air temp sensor kit consists of 4 pieces and should be part of the display unit package at initial purchase. The air temp sensor part number is 885342001.
Good luck...you made a wise decision that will enhance your boating pleasure and safety.