Wow, scratchbuilding a ship as your first model is a tall order...here's what I would suggest (having done this a few times).
You'll need a set of builder's plans, I would suggest looking at Floating Drydock www.floatingdrydock.com or Taubman's Plan Service. You'll need plans that have hull lines. I would also suggest getting a couple of books, John Bowen's Model Ship Building and Mike Ashey's 'Basics of Ship Modeling' (Kalmbach). Select a scale, I would recommend either 1/350 or 1/192, as you have ready access to fittings and detail parts in these scales.
You can build your hull in a conventional method, plank on frame, bread and butter, or you can carve one from a solid piece of wood. If you want a quick method, you can use the following, which I use on my hulls.
Build your frames like you would a conventional ship, using heavy styrene for the 'ribs'. Once you have the skeleton of the hull complete, 'plank' the hull using masking tape...and fill each of the compartments with resin, use slow-curing resin so it doesn't generate as much heat. Once the resin has cured, remove the tape and start wet-sanding. When you see the plastic frames show through, you have the correct contour of the hull.
From there, building the superstructure is relatively simple, using styrene strips and plastic sheet. Fittings such as AA guns, ships' boats, Carley floats, etc., can be taken from another kit. In 1/192, you'll need to purchase each part. Floating Drydock also sells ships' fittings specifically for USN vessels.
It's definitely an ambitious project. Feel free to drop me an email if you have any other questions.
Best of Luck,
Jeff Herne
Associate Editor, FineScale Modeler