I went aftermarket for all of the items that you mentioned. Pricing it out I was able to save about 1,000 on the winch, roof, windshield, and plow setup. I went with Kolpin for the windshield and roof and the installs were fairly easy (though I will caution if you intend on buying the Honda factory soft doors, do not by the Kolpin Pro roof, as you will have to make some modifications to the sides of the roof to get the doors to fit.) KFI winch bracket was easy to install, and the longest part of the Denali Plow install was installing the bolts for the cutting edge and rubber flap.
If you have the dealership install items like the winch and plow, I am fairly certain they will not install them without the prerequisite "attachment kit", which bloats their price quite a bit. Items like the plow and winch have a "prep kit" to the tune of a few hundred bucks each.
At least, that was what I was told at the dealership. It's what prompted me, for the most part, to go aftermarket with almost all of the accessories I have bought for my buggy.