Should I pre-medicate to prevent infective endocarditis?

Depends. In 2007 the american heart association, american college of cardiology, and american dental association downgraded its recommendations based on new research which showed that endocarditis is, in most instances, rarer than then the rare serious side effects of antibiotics. People with artificial valves or certain uncorrected forms of congenital heart disease do need prophylaxis. Others don't.
Depends. Antibiotic prophylaxis recommendations have changed significantly. Talk to your physician or cardiologist.
Depends. It depends on whether the situation your facing is likely to produce significant bacteremia (bacteria in blood), and whether you have a significant structural abnormality of your heart that would make you more susceptible to acquire infective endocarditis.