I'm stepping out of line here to answer these qeeeeeestions
1. Nothing special, actually. When you send in the mix itself, list the artist as the name of your group. Then in the song description, list the members names and individual OCR pages (if applicable). The artist group should automatically be formed based on the information you provide, granted that the mix is accepted. The same thing happened for the Muffins, and I believe the same thing happens for each One Ups mix, Insert Rupee, etc. etc.
2. This SHOULD be in the wiki for projects, but you should send an email to projects@ocremix.org with a project proposal and link to the thread. The proposal is reviewed and then you're contacted about it.