I can offer some tips on directions to follow, but I'm not sure how well they'll pan out. I've had to do some research on the Monitor on a couple of occasions. From 1980 to 1983 I worked as a curator at the Mariners' Museum in Newport News, Viriginia, where the artifacts from the Monitor are being conserved and exhibited. We did an exhibition of artifacts that had been brought up as of that time (a fraction of what's on exhibit now) and I was in charge of tracking down relevant documents that would be appropriate for public display.
The bottom line is that, unfortunately, no complete contemporary set of plans for the Monitor, including all the details of the interior, exists. The nearest thing to such a set is a lovely, hand-tinted 3-view drawing on cloth that apparently was done by John Ericsson, the ship's designer. It includes one longitudinal section and one cross-section, both of which include the interior components. The drawing is in the collection of the American-Swedish Historical Society in Philadelphia. (When I was at the MM I tried to borrow the drawing for our exhibition and was told it was too badly deteriorated to travel. We eventually engineered an agreement whereby the ASHS would lend us the drawing in exchange for our paying the expenses of having it sent to a lab for conservation. We were really happy that we could do that.) I have no idea whether the ASHS has copies of the drawing available for sale, but it's been reproduced quite a few times in books.
Some years after I left the museum the Monitor Marine Sanctuary hired me to design a simple paper model of the ship, for distribution to children's groups. I browsed through all the plans I could find, and eventually concluded that the best available were the ones by Alan B. Chesley. I'm wracking my poor old brain trying to remember the title and author of the book in which they were published, so far without success. If I can think of it later I'll do another post.
There are lots of big questions about the Monitor's appearance. One, surprisingly, concerns the top of the turret. So far as I know, nobody is quite sure whether it was covered with iron plates or an iron grating. The Ericsson plans don't clarify that point. When the ship sank the turret fell off and landed upside down, with the hull overlapping it. As you probably know, the turret was brought up recently, and currently is in conservation at Newport News. I haven't seen it myself, but I have talked to one of the conservators who's inspected it. He told me that the turret roof is so thoroughly covered in concretions that it's still not possible to tell how it's constructed. That's just a prominent example of how tough it is to figure out just what that ship looked like - even with big pieces of it available for physical inspection.
The school where I work now, East Carolina University, has been extensively involved in the Monitor project for quite a few years. I personally haven't had much to do with it, but my friend Brad Rodgers, in the ECU Maritime History Program, is extremely knowledgeable about the subject and the sources of information about the ship. I'm sure he'd be happy to help. His e-mail address is <rodgersb@mail.ecu.edu>.
Sorry to be less than optimistic. This is a fascinating subject, but one that still has a certain amount of mystery surrounding it.