Your current resume and cover letter may have been perfect for impressing your current employer, but if you're looking for a career change, you need to spruce them up to match your ambitions. If you're working in the tech field now and want to move into something more creative, for example, you'll want to change up your resume to focus on your creative skills. This is called creating a "targeted resume." Do some research to see what key skills your ideal employers are looking for, and feature them prominently in your resume.
The same goes for your cover letter. You want to sum up your skills and explain, point by point, why you're the most qualified candidate for the position. If someone from within the company referred you, the cover letter is a good place to mention it. Many companies give extra weight to applicants who have an internal referral.