Talked with the Coast Guard a couple of times this morning. They did seem very helpful.
Some new info came to light though. The boat has indeed been documented previously, just not currently. So that helps because I don't need the simplified measurements form. So basically, I only need:
a) If we document right now - USCG application, seller's registration or title, and bill of sale.
b) If we decide to first title in MD and switch to USCG later - USCG application and my own MD registration or title.
We might go with option B only because since I'm handling the documentation myself, if there are any paperwork problems, I don't have to worry that the boat's not titled legally. Then I can take my own sweet time and switch over.
Thanks again for the help everyone. I'll let you know how it goes!