These seats are genuine leather, aren't they? If you accidentally dirty them, it could be a real problem.
Literal
This seat, genuine-leather [copula-です] [confirm-ね]. Mistakenly dirty-[conditional-と] terrible-thing [to-に] become-[seems-そうです].
本革 'genuine leather' (本 'real/genuine' + 革 'leather') contrasts with 合皮 'synthetic leather.' 間違って 'by mistake' is the te-form of 間違う used as an adverb. 大変なことになりそうです combines なる (become) + そう (seems) to express an anticipated negative outcome — the ~そう is conjecture from the situation rather than from appearance.