Bob,
We are local. I have a few of these and am pretty familiar with them. Let's look at it together and I can give you some (talented amateur? Semi-knowledgeable?) advice. Also, if you'd like to shoot one ahorehand, you can try one of mine (except my Navy). Currently my post-war S model is dirty; my girl took it to the range last weekend and has not cleaned it yet! Lets get it dirtier.
A "C" model reduces my interest in paying a lot. Pre-War or "S" models are what you want. Several very desirable features were deleted by then - the long action, and the 1/2 moon front sight, namely. This gun falls more into the "pedestrian post-war" category and unless it's virtually new shouldn't command a big premium, and unless it has original grips, not worth pursing unless it comes very cheaply. K frame magnas from that period in excellent or better condition can fetch $75 to 100 alone, and should be deducted from the gun price unless the gun has the original grips.
pm me if you'd like to talk about it or have someone look at it. OTOH, if you are just looking for a "shooter", and it has the barrel length you want, (4" is the limit of a "fun field gun" to me in a k frame) and it's clean and sober, a sub-$300 price is not too much to pay. Realize, though, if it's a 5" gun that holsters are hard to come by unless custom nowadays. 5" was the most common length then, but not since the early/mid 60s. Here's a 5" M&P, '47 vintage with the long action, I bought fall of 2007, and it came with a custom TX hand-made holster all for $300 and with virtually no use, 99% or better condition. From the classifieds here. Unless you are getting just the gun you want, don't pay $300 for an M&P unless you've done a lot of shopping. With over four million of these made, there are lots out there to choose from, and they come up for sale with stunning regularity.