You have an opportunity to advance your career. (No employer can reasonably argue with this)
While philosophies on resignations and exit interviews vary, here's my dime (inflation )
I'd hand deliver my resignation to the person who hired me or now holds that position. If that person is not available (vacation, etc.) give it to the fill in or the next up the chain.
Of course you express gratitude for your previous job. Same with the exit interview. Even though it's voluntary, do participate, but resist the temptation to vent and be vague, but positive. Remember, the exit interview is a tool designed to benefit the facility, not you. If your management team has been receptive and open to constructive criticism in the past, by all means, point out problem areas.