"The oil is in the store."
Translation:Das Öl ist im Laden.
We need dative with this sentence (see my response to VladAnghel). I believe this changes your 'das Geschäft' to 'dem Geschäft', so you end up with 'Das Öl ist im Geschäft'.
From what I can tell from my very limited experience, Geschäft and Laden can be used interchangeably. I did wonder if the difference was like store or shop or place of business, but I really don't know.