1. Yes, you're able to change both your main character's and your pawn's appearance. Eventually, a man at The Encampment will be standing by Rift Stone where he sells skin color, hair color, and something else I forgot; you use Rift Points to buy them. At Grand Soren, I think you can get hair style change, hair, facials, etc. Then, at the Main Title, you can character edit.
2. The Pawn you create will be your Main Pawn. Yes, he/she will be permanent. If he/she dies (ie: disappears after being down for too long), you can pick him/her up in the Rift Stone. I believe you have the option to venture solo, I haven't tried yet, so I'm not sure. You're also able to have 2 other pawns join your party, making it 4 people total (in case you didn't know).
3. I recommend saving a lot. Actually.. A LOT. Because monsters can get pretty tough. If you venture enough where monsters almost kill you in one hit.. I recommend waiting 'til you get at a higher level.
I don't know how else to answer, so hope this helps.
EDIT:
Also, bring curatives for yourself. You'll need them. Eventually you'll find a few Healing Springs through Gransys. I recommend bringing Empty Bottles. You can fill them up like you do w water and oil. They heal the team.