Frogger,
Welcome to the forum! Your wife has a pretty common, but still wonderful piece of Smith and Wesson art, that seems to be in very..... very.... nice original condition.
These are wonderful range, or home defense guns, that will last a lifetime. A 38 revolver is perfect for a beginning shooter, either man or woman. Since your wife has not shot this gun, yet..... hopefully you can get her to pull the trigger, one of these days. Unlike a Semi-Auto, there is no heavy slide to have to rack, so they are easy to load for anyone with reduced strength in their hands.
Best of all.... A revolver will not deposit hot brass down the front of her shirt. Yes it does happen...
If you can find them, a box of 148 grain wad cutters is probably the perfect thing to break her in on, as they are light loaded, and accurate.
Any 38 special ammo will get the job done, but the +P ammo is un-necessary, for range duty.
My wife has a Mod 10.... the same gun, but with fixed sights for her bedside gun.. She shoots it well, and most importantly, has a flawless understanding of how to safely load and unload it.
If you have the original pieces that were mentioned, that is great, and would absolutely increase the value, to a collector.
However, If you don't, and want to return the gun to original style grips, there are a lot of grips on Ebay.
Also a great place to look, is in the Box-O-Parts, at an older gun shop. About every shop that has been around anytime will have a box or two of misc parts that some times includes take off grips, extra mags, and other items that often are too good to toss, but they are not sure what to do with. Of course you have to get their before others, from this Forum get there..
A nice set of original style grips should be able to be purchased for less than $50.00, and would return the 15 to its original beauty.
Enjoy that gun in good heath!