Sheephorn Road: I thought this road was in great shape, the early part of the road goes through some ranches then passes a winter closure gate into a patch of public land, then passes through the south end of a ranch before going public again near the turnoff for FS 442. You need 4WD for FS 442, but should be able to continue in a sedan along 401. When I climbed Piney Peak I drove past this turn off to around 9,900' and bushwhacked up a small valley to Walters Lake to pick up 442 then FS 784 to McCord Pass and up Piney's NW Ridge. Also walked the 784 road to Cottonwood Peak (another ranked 11er) and then back to my car.
The road gets a little rougher after where I parked and its best to go back the way you went. I had my XTerra at the time and drove over to pick up UN 10362 on FS 444, but you need 4WD for that one, that road is steep and rocky where it turns north to Cottonwood Mesa Spring. Also, the 401 road loops back on itself as FS 402, but that road is not good for a standard sedan, near Little Cottonwood Res is gets a bit steep and had some mud ruts that if wet would be too slick for 2WD.
Muddy Pass Road: From CO 131 to Muddy Pass is just a 2WD gravel road and in good shape, but I have not driven it down to the Piney River. There is a road (FS 701) that connects along the backside of Red and White Mountain to the Red Sandstone Road and Piney Lake. That road is bumpy in a few spots, but should be good for your sedan. It won't get you to Piney Ridge though, you are better off using the Sheephorn Road as described above.
Have fun, that is a cool part of the Gore Range that is less traveled (outside of hunting season anyway). Piney Peak has great views to the south, and some cool cliffs on its NE face that the McCord Pass road passes underneath. An underrated peak, but most 11ers usually are!