New Remington Express defense guns are not much more than the used Wingmaster.
The Wingmaster is a nicer gun, and is essentially the same gun as the Remington Police model.
If you're a "do-it-yourself" guy, it's fairly easy to convert a Wingmaster into a great HD gun.
About the only problem in a conversion is replacing the front bead or sight, which is better done by a gunsmith.
There are many people who don't even bother with replacing the sight.
Cutting a barrel is easy, and if you decide to do it, let me know and I'll post a set of instructions that make a cut-down job easy enough that anyone can get a perfect outcome.
New magazine extensions by Choate cost around $40.00, and are simple to install.
The older gun that takes 2 3/4" shells-only is no handicap.
Very few people use 3" Magnum shells for HD due to the STIFF recoil, which makes followup shots slower.
In fact, many police and civilian shooters are going to the Reduced Recoil ammo for this reason.
Bottom line: Simply buying a Remington HD is the most easy, and the gun is ready to go right out of the box with no changes or accessories necessary, or really advisable.
The older Wingmaster is a smoother, better finished gun, that can be converted to basically the same thing as a Police gun, but does require some effort and buying a magazine extension IF you want one.