Any designer will tell you that typeface choices are important. The right typeface can bring out the personality in the piece and make it really stand out in the readers mind. In terms of readability, as long as the typeface's letters are easy to identify, you're good to go.

On that note though: BEWARE OVERLY DECORATIVE TYPEFACES

- If an overly decorative typeface is used for instructions, the perceived difficulty of the instructions themselves is actually increased.

If you want people to actually follow the instructions you're giving them, you need to make it as approachable and friendly as possible (such as Arial, Helvetica etc)