If you need a general idea on my skill level in Fire Emblem, FE9's Hard Mode gave me more than a few problems, though I eventually got through it.
It's a little more difficult than that, but unless you're getting the Japanese version of the game, you can use Battle Saves to make a permanent save in the middle of a fight anytime you wish. As such, you can save before doing anything dangerous and try again as many times as you'd like if you fail (plus it makes restarting less of a hassle since you won't have to restart the whole mission over if you have another battle save to start from).