Is it possible to determine the amount of hours on the EX-1? I'm considering purchasing one -maybe a used one if I can establish how much it's been used.

Go to the Others menu, scroll down to Hours Meter. Look at Hours (Sys).

Hours of use is important on a used tape drive camera. Drive repairs are expensive and drives don't last very long.

Hours don't matter much on these solid state cameras. No moving tape drive parts.

Much more important to evaluate the picture and overall physical condition.