1. We bought ours too long ago for me to remember what we needed; Contact the National Vessel Documentation Center (USCG National Vessel Documentation Center - POC Page
) 304-271-2400 for their requirements. They're generally pretty helpful on the phone.
2. Maryland DNR are generally easier to deal with in person than by phone, but here's their link: Maryland Department of Natural Resources - Boating
If you're documented you won't need to put an MC number on the boat, but you'll still need the registration sticker. Cost is nominal $10 I think.