Learn Russian: В отличие от вас, этот механик знает, как чинить кузов. - Unlike you, this mechanic knows how to repair the car body.

The compound preposition в отличие от means unlike or in contrast to, and the от part tells you it must be followed by the Genitive case. Here, вас is the Genitive form of the pronoun вы.

Is the comma after вас required?

Yes. In Russian punctuation, phrases starting with в отличие от are almost always set off by commas to clearly separate the contrasted element from the main clause.

Why does the sentence use the imperfective verb чинить instead of the perfective починить?

The imperfective чинить is used because the sentence describes a general skill or knowledge (knowing how to do bodywork in general). If the mechanic were focusing on finishing one specific, immediate repair job, you would see the perfective починить instead.

What case is the word кузов in? It looks like it is in the Nominative case.

It is actually in the Accusative case because it is the direct object being repaired. Since кузов (car body) is an inanimate masculine noun, its Accusative form looks exactly the same as its Nominative (dictionary) form.