Entire sentence in parentheses

I am formatting a new book for my company and ran into a problem.

There is a sentence that reads:

Before beginning, watch Part I in the DVD series, God & the History of Art. (If available as part of your program.)

That the author wants me to change to:

(Before beginning, watch Part I in the DVD series, God & the History of Art. If available as part of your program.)

This sentence is one line, not part of a paragraph.

Is it right to surround an entire standalone sentence with parentheses?

Yes, provided it's all parenthetical material.

This appears to qualify. However, I'd make it all one sentence and add in the deleted it for clarity:

(Before beginning, watch Part I of the DVD series God & the History of Art, if it is available as part of your program.)