Hello and welcome!
I'm one of the New Player Marshals from the Southern Minnesota chapter!
I'll address your concerns, again echoing a couple things Luke already mentioned:
If you pre-register (let us know you're coming), NPCing is free. Monster Camp will give you everything for costuming, etc. but also read what you should bring to events as an NPC here:
http://mnalliance.com/new-players/faqs/ ... o-an-event
If you post the need for a ride on the SoMN section of these boards, people are usually able to arrange carpools and just ask for a gas contribution.
If you are 16, you can fully participate with a signed parent permission form. (16 is the minimum age)
We train in new players on the basics before each game, with continued training and practice through out the event.
For how to get started, check out:
http://mnalliance.com/new-players/faqs/getting-started/
Our next event is this weekend, so while it is short notice, as an NPC there isn't really much you need to prepare, so I'd encourage you to make it if you can.
If you have any further questions, send an email to
info@mnalliance.com and I'll get you in contact with one of our New Player Marshals to work one on one with you.
Welcome again and I hope to see you at a game soon!