intergrated

Hello? I installed an intergrated recirculating hood while repairing the kitchen this time, and I have a question. I installed a hood in the cabinet, should I make a hole through which air flows out of the cabinet? Some people say they don't need it, and others say they need it.

Does anyone know of a good product for repairing the enamel where an integrated oven mounts to the unit? I bought an ex-display unit and someone has managed to damage it in the process of removal Enamel is a gloss grey and I don't need much but not sure which products are suitable and not too...