Although the Glencoe Oregon can be built into a beautiful and impressive model, I would agree with EdGrune that it is not for a beginner - even if you have a complete aftermarket PE set, there are still some missing details that need adding/scratchbuilding (turret roof vents, boat oars, etc.), modifying/reworking many of the plastic parts to add PE detail requires a fair amount of skill, and most of the kit parts require a lot of cleanup, sanding, filler etc. Basically wait until you've got a reasonable amount of experience working with PE and making simple modifications and scratchbuilt additions to styrene parts with Evergreen etc.
For reference, photos of the 1/48 Smithsonian museum model (available on the Internet, can't remember the URL but a Google search would probably find them) will help. An old issue of FSM (can't remember the year - 2002?) also had a good article on detailing the Oregon.
However, if built "out of the box" it'll still look quite nice, particularly if you add railings - but the poorly moulded parts (lots of flash/mould lines to clean up) and poor fit might be frustrating.
Regarding the railings, 1/200 scale would almost certainly look OK, for a start the scale of the kit is actually slightly larger than the "1/225" on the box (something like 1/215), secondly, unless you know exactly how tall the original railings are supposed to be, the 7% approx. height difference won't be very noticeable - IMHO at least.
Another tip - the Tom's Modelworks PE set is MUCH cheaper than the Gold Medal one, although the latter has the advantage of also including parts for the Revell USS Olympia.
A good choice for a first "pre-dreadnought" battleship would be either Zvezda's "Borodino" (Imperial Russian) or Hasegawa's "Mikasa" (Japanese) - these are a significantly smaller scale (1/350) but being much newer toolings have much better fit, accuracy and detail. Zvezda's "Varyag" and Revell's "SMS Emden" are excellent kits of cruisers from the same era, also in 1/350.