I recently got a 3DS about a month ago so I just went through this same process/
2. I'd also go with Mario
3. Most (if not all) games are available for download on the store (Zelda, Bravely, and Fire Emblem all def are)
4. You can upgrade all the way up to a 32gb card. From what I understand that nets you around 200k blocks, most games are around 4k blocks.
5. Fire Emblem, Snake Eater 3D, any DS games you might be interested in