Conver jpg. to Greyscale / Vector To Print On T-Shirts 10"

See image attached...it was the highest res image I could find for my client.....I need to convert to be able to print a one colour silk-screen print on t-shirts....more than likely greyscale. Size of print to be 10" in proportion. Need to put one line (3 words) of text underneath to describe vessel in cool font..maybe keyline. Also front of t-shirt design...just text for event...can provide to you through Freelancer communications. "Custoners Name" Family & Friends Cruise 2011....something like that, maybe a nice distressed look. Full front design for t-shirt will be 4" wide - 10" max customer needs to approve my layout.