Here are some Tips for you, since this is your first time (it was my first FE too, and i played and beat it on Normal, but I had to restart over 1/2 of the way through because i totally screwed up my team)
1. for units that only get 1 exp when attacking, unequip them and use them as tanks
2. Move slowly, and highlight the enemy units to make sure you didn't leave anyone who is weak in a bad spot.
3. Don't always attack, sometimes just let them come at you and heal yourself. It wears down the enemy.
4. You can recruit Aran by talking to him, which you do by standing next to him and hitting the talk command. (doh... I spent so long trying to beat that level and I didn't know you could recruit one extra unit)